diff --git a/ruma-identifiers-validation/Cargo.toml b/ruma-identifiers-validation/Cargo.toml
new file mode 100644
index 00000000..81cf8bf1
--- /dev/null
+++ b/ruma-identifiers-validation/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "ruma-identifiers-validation"
+description = "Validation logic for ruma-identifiers and ruma-identifiers-macros"
+documentation = "https://docs.rs/ruma-identifiers"
+homepage = "https://www.ruma.io/"
+repository = "https://github.com/ruma/ruma"
+authors = [
+    "Jimmy Cuadra <jimmy@jimmycuadra.com>",
+    "Jonas Platte <jplatte@posteo.de>",
+]
+license = "MIT"
+version = "0.1.0"
+edition = "2018"
+
+[dependencies]
+strum = { version = "0.18.0", features = ["derive"] }
diff --git a/ruma-identifiers-validation/LICENSE b/ruma-identifiers-validation/LICENSE
new file mode 100644
index 00000000..de62627d
--- /dev/null
+++ b/ruma-identifiers-validation/LICENSE
@@ -0,0 +1,20 @@
+Copyright (c) 2016 Jimmy Cuadra
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
diff --git a/ruma-identifiers-validation/src/device_key_id.rs b/ruma-identifiers-validation/src/device_key_id.rs
new file mode 100644
index 00000000..596651c4
--- /dev/null
+++ b/ruma-identifiers-validation/src/device_key_id.rs
@@ -0,0 +1,13 @@
+use std::{num::NonZeroU8, str::FromStr};
+
+use crate::{key_algorithms::DeviceKeyAlgorithm, Error};
+
+pub fn validate(s: &str) -> Result<NonZeroU8, Error> {
+    let colon_idx = NonZeroU8::new(s.find(':').ok_or(Error::MissingDeviceKeyDelimiter)? as u8)
+        .ok_or(Error::UnknownKeyAlgorithm)?;
+
+    DeviceKeyAlgorithm::from_str(&s[0..colon_idx.get() as usize])
+        .map_err(|_| Error::UnknownKeyAlgorithm)?;
+
+    Ok(colon_idx)
+}
diff --git a/ruma-identifiers/src/error.rs b/ruma-identifiers-validation/src/error.rs
similarity index 100%
rename from ruma-identifiers/src/error.rs
rename to ruma-identifiers-validation/src/error.rs
diff --git a/ruma-identifiers-validation/src/event_id.rs b/ruma-identifiers-validation/src/event_id.rs
new file mode 100644
index 00000000..a6481399
--- /dev/null
+++ b/ruma-identifiers-validation/src/event_id.rs
@@ -0,0 +1,13 @@
+use std::num::NonZeroU8;
+
+use crate::{parse_id, validate_id, Error};
+
+pub fn validate(s: &str) -> Result<Option<NonZeroU8>, Error> {
+    Ok(match s.contains(':') {
+        true => Some(parse_id(s, &['$'])?),
+        false => {
+            validate_id(s, &['$'])?;
+            None
+        }
+    })
+}
diff --git a/ruma-identifiers/src/key_algorithms.rs b/ruma-identifiers-validation/src/key_algorithms.rs
similarity index 100%
rename from ruma-identifiers/src/key_algorithms.rs
rename to ruma-identifiers-validation/src/key_algorithms.rs
diff --git a/ruma-identifiers-validation/src/lib.rs b/ruma-identifiers-validation/src/lib.rs
new file mode 100644
index 00000000..85785373
--- /dev/null
+++ b/ruma-identifiers-validation/src/lib.rs
@@ -0,0 +1,56 @@
+pub mod device_key_id;
+pub mod error;
+pub mod event_id;
+pub mod key_algorithms;
+pub mod room_alias_id;
+pub mod room_id;
+pub mod room_id_or_alias_id;
+pub mod room_version_id;
+pub mod server_key_id;
+pub mod server_name;
+pub mod user_id;
+
+use std::num::NonZeroU8;
+
+pub use error::Error;
+
+/// All identifiers must be 255 bytes or less.
+const MAX_BYTES: usize = 255;
+
+/// The minimum number of characters an ID can be.
+///
+/// This is an optimization and not required by the spec. The shortest possible valid ID is a sigil
+/// + a single character local ID + a colon + a single character hostname.
+const MIN_CHARS: usize = 4;
+
+/// Checks if an identifier is valid.
+fn validate_id(id: &str, valid_sigils: &[char]) -> Result<(), Error> {
+    if id.len() > MAX_BYTES {
+        return Err(Error::MaximumLengthExceeded);
+    }
+
+    if id.len() < MIN_CHARS {
+        return Err(Error::MinimumLengthNotSatisfied);
+    }
+
+    if !valid_sigils.contains(&id.chars().next().unwrap()) {
+        return Err(Error::MissingSigil);
+    }
+
+    Ok(())
+}
+
+/// Checks an identifier that contains a localpart and hostname for validity,
+/// and returns the index of the colon that separates the two.
+fn parse_id(id: &str, valid_sigils: &[char]) -> Result<NonZeroU8, Error> {
+    validate_id(id, valid_sigils)?;
+
+    let colon_idx = id.find(':').ok_or(Error::MissingDelimiter)?;
+    if colon_idx < 2 {
+        return Err(Error::InvalidLocalPart);
+    }
+
+    server_name::validate(&id[colon_idx + 1..])?;
+
+    Ok(NonZeroU8::new(colon_idx as u8).unwrap())
+}
diff --git a/ruma-identifiers-validation/src/room_alias_id.rs b/ruma-identifiers-validation/src/room_alias_id.rs
new file mode 100644
index 00000000..48ab1220
--- /dev/null
+++ b/ruma-identifiers-validation/src/room_alias_id.rs
@@ -0,0 +1,7 @@
+use std::num::NonZeroU8;
+
+use crate::{parse_id, Error};
+
+pub fn validate(s: &str) -> Result<NonZeroU8, Error> {
+    parse_id(s, &['#'])
+}
diff --git a/ruma-identifiers-validation/src/room_id.rs b/ruma-identifiers-validation/src/room_id.rs
new file mode 100644
index 00000000..cb2fa3f0
--- /dev/null
+++ b/ruma-identifiers-validation/src/room_id.rs
@@ -0,0 +1,7 @@
+use std::num::NonZeroU8;
+
+use crate::{parse_id, Error};
+
+pub fn validate(s: &str) -> Result<NonZeroU8, Error> {
+    parse_id(s, &['!'])
+}
diff --git a/ruma-identifiers-validation/src/room_id_or_alias_id.rs b/ruma-identifiers-validation/src/room_id_or_alias_id.rs
new file mode 100644
index 00000000..e477d164
--- /dev/null
+++ b/ruma-identifiers-validation/src/room_id_or_alias_id.rs
@@ -0,0 +1,7 @@
+use std::num::NonZeroU8;
+
+use crate::{parse_id, Error};
+
+pub fn validate(s: &str) -> Result<NonZeroU8, Error> {
+    parse_id(s, &['#', '!'])
+}
diff --git a/ruma-identifiers-validation/src/room_version_id.rs b/ruma-identifiers-validation/src/room_version_id.rs
new file mode 100644
index 00000000..894a9bdd
--- /dev/null
+++ b/ruma-identifiers-validation/src/room_version_id.rs
@@ -0,0 +1,14 @@
+use crate::Error;
+
+/// Room version identifiers cannot be more than 32 code points.
+const MAX_CODE_POINTS: usize = 32;
+
+pub fn validate(s: &str) -> Result<(), Error> {
+    if s.is_empty() {
+        Err(Error::MinimumLengthNotSatisfied)
+    } else if s.chars().count() > MAX_CODE_POINTS {
+        Err(Error::MaximumLengthExceeded)
+    } else {
+        Ok(())
+    }
+}
diff --git a/ruma-identifiers-validation/src/server_key_id.rs b/ruma-identifiers-validation/src/server_key_id.rs
new file mode 100644
index 00000000..b3982acd
--- /dev/null
+++ b/ruma-identifiers-validation/src/server_key_id.rs
@@ -0,0 +1,30 @@
+use std::{num::NonZeroU8, str::FromStr};
+
+use crate::{key_algorithms::ServerKeyAlgorithm, Error};
+
+pub fn validate(s: &str) -> Result<NonZeroU8, Error> {
+    let colon_idx = NonZeroU8::new(s.find(':').ok_or(Error::MissingServerKeyDelimiter)? as u8)
+        .ok_or(Error::UnknownKeyAlgorithm)?;
+
+    validate_server_key_algorithm(&s[..colon_idx.get() as usize])?;
+    validate_version(&s[colon_idx.get() as usize + 1..])?;
+
+    Ok(colon_idx)
+}
+
+fn validate_version(version: &str) -> Result<(), Error> {
+    if version.is_empty() {
+        return Err(Error::MinimumLengthNotSatisfied);
+    } else if !version.chars().all(|c| c.is_alphanumeric() || c == '_') {
+        return Err(Error::InvalidCharacters);
+    }
+
+    Ok(())
+}
+
+fn validate_server_key_algorithm(algorithm: &str) -> Result<(), Error> {
+    match ServerKeyAlgorithm::from_str(algorithm) {
+        Ok(_) => Ok(()),
+        Err(_) => Err(Error::UnknownKeyAlgorithm),
+    }
+}
diff --git a/ruma-identifiers-validation/src/server_name.rs b/ruma-identifiers-validation/src/server_name.rs
new file mode 100644
index 00000000..a9888d62
--- /dev/null
+++ b/ruma-identifiers-validation/src/server_name.rs
@@ -0,0 +1,46 @@
+use crate::error::Error;
+
+pub fn validate(server_name: &str) -> Result<(), Error> {
+    use std::net::Ipv6Addr;
+
+    if server_name.is_empty() {
+        return Err(Error::InvalidServerName);
+    }
+
+    let end_of_host = if server_name.starts_with('[') {
+        let end_of_ipv6 = match server_name.find(']') {
+            Some(idx) => idx,
+            None => return Err(Error::InvalidServerName),
+        };
+
+        if server_name[1..end_of_ipv6].parse::<Ipv6Addr>().is_err() {
+            return Err(Error::InvalidServerName);
+        }
+
+        end_of_ipv6 + 1
+    } else {
+        let end_of_host = server_name.find(':').unwrap_or_else(|| server_name.len());
+
+        if server_name[..end_of_host]
+            .bytes()
+            .any(|byte| !(byte.is_ascii_alphanumeric() || byte == b'-' || byte == b'.'))
+        {
+            return Err(Error::InvalidServerName);
+        }
+
+        end_of_host
+    };
+
+    if server_name.len() != end_of_host
+        && (
+            // hostname is followed by something other than ":port"
+            server_name.as_bytes()[end_of_host] != b':'
+            // the remaining characters after ':' are not a valid port
+            || server_name[end_of_host + 1..].parse::<u16>().is_err()
+        )
+    {
+        Err(Error::InvalidServerName)
+    } else {
+        Ok(())
+    }
+}
diff --git a/ruma-identifiers-validation/src/user_id.rs b/ruma-identifiers-validation/src/user_id.rs
new file mode 100644
index 00000000..6362099f
--- /dev/null
+++ b/ruma-identifiers-validation/src/user_id.rs
@@ -0,0 +1,35 @@
+use std::num::NonZeroU8;
+
+use crate::{parse_id, Error};
+
+pub fn validate(s: &str) -> Result<(NonZeroU8, bool), Error> {
+    let colon_idx = parse_id(s, &['@'])?;
+    let localpart = &s[1..colon_idx.get() as usize];
+    let is_historical = localpart_is_fully_comforming(localpart)?;
+
+    Ok((colon_idx, is_historical))
+}
+
+/// Check whether the given user id localpart is valid and fully conforming
+///
+/// Returns an `Err` for invalid user ID localparts, `Ok(false)` for historical user ID localparts
+/// and `Ok(true)` for fully conforming user ID localparts.
+pub fn localpart_is_fully_comforming(localpart: &str) -> Result<bool, Error> {
+    if localpart.is_empty() {
+        return Err(Error::InvalidLocalPart);
+    }
+
+    // See https://matrix.org/docs/spec/appendices#user-identifiers
+    let is_fully_conforming = localpart
+        .bytes()
+        .all(|b| matches!(b, b'0'..=b'9' | b'a'..=b'z' | b'-' | b'.' | b'=' | b'_' | b'/'));
+
+    // If it's not fully conforming, check if it contains characters that are also disallowed
+    // for historical user IDs. If there are, return an error.
+    // See https://matrix.org/docs/spec/appendices#historical-user-ids
+    if !is_fully_conforming && localpart.bytes().any(|b| b < 0x21 || b == b':' || b > 0x7E) {
+        Err(Error::InvalidCharacters)
+    } else {
+        Ok(is_fully_conforming)
+    }
+}
diff --git a/ruma-identifiers/Cargo.toml b/ruma-identifiers/Cargo.toml
index cf1ee9a9..925a55d7 100644
--- a/ruma-identifiers/Cargo.toml
+++ b/ruma-identifiers/Cargo.toml
@@ -1,5 +1,8 @@
 [package]
-authors = ["Jimmy Cuadra <jimmy@jimmycuadra.com>"]
+authors = [
+    "Jimmy Cuadra <jimmy@jimmycuadra.com>",
+    "Jonas Platte <jplatte@posteo.de>",
+]
 categories = ["api-bindings"]
 description = "Resource identifiers for Matrix."
 documentation = "https://docs.rs/ruma-identifiers"
@@ -22,9 +25,10 @@ default = ["serde"]
 [dependencies]
 either = { version = "1.5.3", optional = true }
 rand = { version = "0.7.3", optional = true }
+ruma-identifiers-validation = { version = "0.1.0", path = "../ruma-identifiers-validation" }
 serde = { version = "1.0.114", optional = true, features = ["derive"] }
 strum = { version = "0.18.0", features = ["derive"] }
 
 [dev-dependencies]
 matches = "0.1.8"
-serde_json = "1.0.56"
+serde_json = "1.0.57"
diff --git a/ruma-identifiers/src/device_key_id.rs b/ruma-identifiers/src/device_key_id.rs
index 284bb4e5..491dbd42 100644
--- a/ruma-identifiers/src/device_key_id.rs
+++ b/ruma-identifiers/src/device_key_id.rs
@@ -1,8 +1,11 @@
 //! Identifiers for device keys for end-to-end encryption.
 
-use crate::{error::Error, key_algorithms::DeviceKeyAlgorithm, DeviceId};
 use std::{num::NonZeroU8, str::FromStr};
 
+use ruma_identifiers_validation::{key_algorithms::DeviceKeyAlgorithm, Error};
+
+use crate::DeviceId;
+
 /// A key algorithm and a device id, combined with a ':'
 #[derive(Clone, Debug)]
 pub struct DeviceKeyId {
@@ -26,14 +29,7 @@ fn try_from<S>(key_id: S) -> Result<DeviceKeyId, Error>
 where
     S: AsRef<str> + Into<Box<str>>,
 {
-    let key_str = key_id.as_ref();
-    let colon_idx =
-        NonZeroU8::new(key_str.find(':').ok_or(Error::MissingDeviceKeyDelimiter)? as u8)
-            .ok_or(Error::UnknownKeyAlgorithm)?;
-
-    DeviceKeyAlgorithm::from_str(&key_str[0..colon_idx.get() as usize])
-        .map_err(|_| Error::UnknownKeyAlgorithm)?;
-
+    let colon_idx = ruma_identifiers_validation::device_key_id::validate(key_id.as_ref())?;
     Ok(DeviceKeyId { full_id: key_id.into(), colon_idx })
 }
 
@@ -43,11 +39,11 @@ common_impls!(DeviceKeyId, try_from, "Device key ID with algorithm and device ID
 mod test {
     use std::convert::TryFrom;
 
+    use ruma_identifiers_validation::{key_algorithms::DeviceKeyAlgorithm, Error};
     #[cfg(feature = "serde")]
     use serde_json::{from_value as from_json_value, json, to_value as to_json_value};
 
     use super::DeviceKeyId;
-    use crate::{error::Error, key_algorithms::DeviceKeyAlgorithm};
 
     #[test]
     fn convert_device_key_id() {
diff --git a/ruma-identifiers/src/event_id.rs b/ruma-identifiers/src/event_id.rs
index c030f6ae..46856568 100644
--- a/ruma-identifiers/src/event_id.rs
+++ b/ruma-identifiers/src/event_id.rs
@@ -2,7 +2,7 @@
 
 use std::{convert::TryFrom, num::NonZeroU8};
 
-use crate::{error::Error, parse_id, validate_id, ServerName};
+use crate::{Error, ServerName};
 
 /// A Matrix event ID.
 ///
@@ -91,15 +91,8 @@ fn try_from<S>(event_id: S) -> Result<EventId, Error>
 where
     S: AsRef<str> + Into<Box<str>>,
 {
-    if event_id.as_ref().contains(':') {
-        let colon_idx = parse_id(event_id.as_ref(), &['$'])?;
-
-        Ok(EventId { full_id: event_id.into(), colon_idx: Some(colon_idx) })
-    } else {
-        validate_id(event_id.as_ref(), &['$'])?;
-
-        Ok(EventId { full_id: event_id.into(), colon_idx: None })
-    }
+    let colon_idx = ruma_identifiers_validation::event_id::validate(event_id.as_ref())?;
+    Ok(EventId { full_id: event_id.into(), colon_idx })
 }
 
 common_impls!(EventId, try_from, "a Matrix event ID");
@@ -112,7 +105,7 @@ mod tests {
     use serde_json::{from_str, to_string};
 
     use super::EventId;
-    use crate::error::Error;
+    use crate::Error;
 
     #[test]
     fn valid_original_event_id() {
diff --git a/ruma-identifiers/src/lib.rs b/ruma-identifiers/src/lib.rs
index 9ec58a63..f797beb8 100644
--- a/ruma-identifiers/src/lib.rs
+++ b/ruma-identifiers/src/lib.rs
@@ -9,25 +9,21 @@
 )]
 #![cfg_attr(docsrs, feature(doc_cfg))]
 
-use std::{convert::TryFrom, num::NonZeroU8};
+use std::convert::TryFrom;
 
 #[cfg(feature = "serde")]
 use serde::de::{self, Deserialize as _, Deserializer, Unexpected};
 
 #[doc(inline)]
 pub use crate::{
-    device_id::DeviceId,
-    device_key_id::DeviceKeyId,
+    device_id::DeviceId, device_key_id::DeviceKeyId, event_id::EventId, room_alias_id::RoomAliasId,
+    room_id::RoomId, room_id_or_room_alias_id::RoomIdOrAliasId, room_version_id::RoomVersionId,
+    server_key_id::ServerKeyId, server_name::ServerName, user_id::UserId,
+};
+#[doc(inline)]
+pub use ruma_identifiers_validation::{
     error::Error,
-    event_id::EventId,
     key_algorithms::{DeviceKeyAlgorithm, ServerKeyAlgorithm},
-    room_alias_id::RoomAliasId,
-    room_id::RoomId,
-    room_id_or_room_alias_id::RoomIdOrAliasId,
-    room_version_id::RoomVersionId,
-    server_key_id::ServerKeyId,
-    server_name::ServerName,
-    user_id::UserId,
 };
 
 #[macro_use]
@@ -37,9 +33,7 @@ pub mod device_id;
 pub mod user_id;
 
 mod device_key_id;
-mod error;
 mod event_id;
-mod key_algorithms;
 mod room_alias_id;
 mod room_id;
 mod room_id_or_room_alias_id;
@@ -55,14 +49,6 @@ pub fn is_valid_server_name(name: &str) -> bool {
     <&ServerName>::try_from(name).is_ok()
 }
 
-/// All identifiers must be 255 bytes or less.
-const MAX_BYTES: usize = 255;
-/// The minimum number of characters an ID can be.
-///
-/// This is an optimization and not required by the spec. The shortest possible valid ID is a sigil
-/// + a single character local ID + a colon + a single character hostname.
-const MIN_CHARS: usize = 4;
-
 /// Generates a random identifier localpart.
 #[cfg(feature = "rand")]
 fn generate_localpart(length: usize) -> Box<str> {
@@ -74,38 +60,6 @@ fn generate_localpart(length: usize) -> Box<str> {
         .into_boxed_str()
 }
 
-/// Checks if an identifier is valid.
-fn validate_id(id: &str, valid_sigils: &[char]) -> Result<(), Error> {
-    if id.len() > MAX_BYTES {
-        return Err(Error::MaximumLengthExceeded);
-    }
-
-    if id.len() < MIN_CHARS {
-        return Err(Error::MinimumLengthNotSatisfied);
-    }
-
-    if !valid_sigils.contains(&id.chars().next().unwrap()) {
-        return Err(Error::MissingSigil);
-    }
-
-    Ok(())
-}
-
-/// Checks an identifier that contains a localpart and hostname for validity,
-/// and returns the index of the colon that separates the two.
-fn parse_id(id: &str, valid_sigils: &[char]) -> Result<NonZeroU8, Error> {
-    validate_id(id, valid_sigils)?;
-
-    let colon_idx = id.find(':').ok_or(Error::MissingDelimiter)?;
-    if colon_idx < 2 {
-        return Err(Error::InvalidLocalPart);
-    }
-
-    server_name::validate(&id[colon_idx + 1..])?;
-
-    Ok(NonZeroU8::new(colon_idx as u8).unwrap())
-}
-
 /// Deserializes any type of id using the provided TryFrom implementation.
 ///
 /// This is a helper function to reduce the boilerplate of the Deserialize implementations.
diff --git a/ruma-identifiers/src/macros.rs b/ruma-identifiers/src/macros.rs
index 600949a9..01c69c8c 100644
--- a/ruma-identifiers/src/macros.rs
+++ b/ruma-identifiers/src/macros.rs
@@ -55,7 +55,7 @@ macro_rules! common_impls {
         }
 
         impl ::std::convert::TryFrom<&str> for $id {
-            type Error = crate::error::Error;
+            type Error = crate::Error;
 
             fn try_from(s: &str) -> Result<Self, Self::Error> {
                 $try_from(s)
@@ -63,7 +63,7 @@ macro_rules! common_impls {
         }
 
         impl ::std::convert::TryFrom<String> for $id {
-            type Error = crate::error::Error;
+            type Error = crate::Error;
 
             fn try_from(s: String) -> Result<Self, Self::Error> {
                 $try_from(s)
diff --git a/ruma-identifiers/src/room_alias_id.rs b/ruma-identifiers/src/room_alias_id.rs
index 1242134f..7478a6ac 100644
--- a/ruma-identifiers/src/room_alias_id.rs
+++ b/ruma-identifiers/src/room_alias_id.rs
@@ -2,7 +2,7 @@
 
 use std::{convert::TryFrom, num::NonZeroU8};
 
-use crate::{error::Error, parse_id, server_name::ServerName};
+use crate::{server_name::ServerName, Error};
 
 /// A Matrix room alias ID.
 ///
@@ -38,13 +38,12 @@ impl RoomAliasId {
 /// Attempts to create a new Matrix room alias ID from a string representation.
 ///
 /// The string must include the leading # sigil, the alias, a literal colon, and a server name.
-fn try_from<S>(room_id: S) -> Result<RoomAliasId, Error>
+fn try_from<S>(room_alias_id: S) -> Result<RoomAliasId, Error>
 where
     S: AsRef<str> + Into<Box<str>>,
 {
-    let colon_idx = parse_id(room_id.as_ref(), &['#'])?;
-
-    Ok(RoomAliasId { full_id: room_id.into(), colon_idx })
+    let colon_idx = ruma_identifiers_validation::room_alias_id::validate(room_alias_id.as_ref())?;
+    Ok(RoomAliasId { full_id: room_alias_id.into(), colon_idx })
 }
 
 common_impls!(RoomAliasId, try_from, "a Matrix room alias ID");
@@ -57,7 +56,7 @@ mod tests {
     use serde_json::{from_str, to_string};
 
     use super::RoomAliasId;
-    use crate::error::Error;
+    use crate::Error;
 
     #[test]
     fn valid_room_alias_id() {
diff --git a/ruma-identifiers/src/room_id.rs b/ruma-identifiers/src/room_id.rs
index 5743fb90..e2c69516 100644
--- a/ruma-identifiers/src/room_id.rs
+++ b/ruma-identifiers/src/room_id.rs
@@ -2,7 +2,7 @@
 
 use std::{convert::TryFrom, num::NonZeroU8};
 
-use crate::{error::Error, parse_id, ServerName};
+use crate::{Error, ServerName};
 
 /// A Matrix room ID.
 ///
@@ -58,8 +58,7 @@ fn try_from<S>(room_id: S) -> Result<RoomId, Error>
 where
     S: AsRef<str> + Into<Box<str>>,
 {
-    let colon_idx = parse_id(room_id.as_ref(), &['!'])?;
-
+    let colon_idx = ruma_identifiers_validation::room_id::validate(room_id.as_ref())?;
     Ok(RoomId { full_id: room_id.into(), colon_idx })
 }
 
@@ -73,7 +72,7 @@ mod tests {
     use serde_json::{from_str, to_string};
 
     use super::RoomId;
-    use crate::error::Error;
+    use crate::Error;
 
     #[test]
     fn valid_room_id() {
diff --git a/ruma-identifiers/src/room_id_or_room_alias_id.rs b/ruma-identifiers/src/room_id_or_room_alias_id.rs
index 60e89bd7..05f13ce6 100644
--- a/ruma-identifiers/src/room_id_or_room_alias_id.rs
+++ b/ruma-identifiers/src/room_id_or_room_alias_id.rs
@@ -2,7 +2,7 @@
 
 use std::{convert::TryFrom, hint::unreachable_unchecked, num::NonZeroU8};
 
-use crate::{error::Error, parse_id, server_name::ServerName, RoomAliasId, RoomId};
+use crate::{server_name::ServerName, Error, RoomAliasId, RoomId};
 
 /// A Matrix room ID or a Matrix room alias ID.
 ///
@@ -89,7 +89,8 @@ fn try_from<S>(room_id_or_alias_id: S) -> Result<RoomIdOrAliasId, Error>
 where
     S: AsRef<str> + Into<Box<str>>,
 {
-    let colon_idx = parse_id(room_id_or_alias_id.as_ref(), &['#', '!'])?;
+    let colon_idx =
+        ruma_identifiers_validation::room_id_or_alias_id::validate(room_id_or_alias_id.as_ref())?;
     Ok(RoomIdOrAliasId { full_id: room_id_or_alias_id.into(), colon_idx })
 }
 
@@ -141,7 +142,7 @@ mod tests {
     use serde_json::{from_str, to_string};
 
     use super::RoomIdOrAliasId;
-    use crate::error::Error;
+    use crate::Error;
 
     #[test]
     fn valid_room_id_or_alias_id_with_a_room_alias_id() {
diff --git a/ruma-identifiers/src/room_version_id.rs b/ruma-identifiers/src/room_version_id.rs
index 94dce568..85cb0fe9 100644
--- a/ruma-identifiers/src/room_version_id.rs
+++ b/ruma-identifiers/src/room_version_id.rs
@@ -9,10 +9,7 @@ use std::{
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 
-use crate::error::Error;
-
-/// Room version identifiers cannot be more than 32 code points.
-const MAX_CODE_POINTS: usize = 32;
+use crate::Error;
 
 /// A Matrix room version ID.
 ///
@@ -231,13 +228,8 @@ where
         "4" => RoomVersionId::Version4,
         "5" => RoomVersionId::Version5,
         custom => {
-            if custom.is_empty() {
-                return Err(Error::MinimumLengthNotSatisfied);
-            } else if custom.chars().count() > MAX_CODE_POINTS {
-                return Err(Error::MaximumLengthExceeded);
-            } else {
-                RoomVersionId::Custom(CustomRoomVersion(room_version_id.into()))
-            }
+            ruma_identifiers_validation::room_version_id::validate(custom)?;
+            RoomVersionId::Custom(CustomRoomVersion(room_version_id.into()))
         }
     };
 
@@ -245,7 +237,7 @@ where
 }
 
 impl TryFrom<&str> for RoomVersionId {
-    type Error = crate::error::Error;
+    type Error = crate::Error;
 
     fn try_from(s: &str) -> Result<Self, Error> {
         try_from(s)
@@ -253,7 +245,7 @@ impl TryFrom<&str> for RoomVersionId {
 }
 
 impl TryFrom<String> for RoomVersionId {
-    type Error = crate::error::Error;
+    type Error = crate::Error;
 
     fn try_from(s: String) -> Result<Self, Error> {
         try_from(s)
@@ -314,7 +306,7 @@ mod tests {
     use serde_json::{from_str, to_string};
 
     use super::RoomVersionId;
-    use crate::error::Error;
+    use crate::Error;
 
     #[test]
     fn valid_version_1_room_version_id() {
diff --git a/ruma-identifiers/src/server_key_id.rs b/ruma-identifiers/src/server_key_id.rs
index 448c0bfa..efb6d168 100644
--- a/ruma-identifiers/src/server_key_id.rs
+++ b/ruma-identifiers/src/server_key_id.rs
@@ -2,7 +2,7 @@
 
 use std::{num::NonZeroU8, str::FromStr};
 
-use crate::{error::Error, key_algorithms::ServerKeyAlgorithm};
+use ruma_identifiers_validation::{key_algorithms::ServerKeyAlgorithm, Error};
 
 /// Key identifiers used for homeserver signing keys.
 #[derive(Clone, Debug)]
@@ -27,37 +27,12 @@ fn try_from<S>(key_id: S) -> Result<ServerKeyId, Error>
 where
     S: AsRef<str> + Into<Box<str>>,
 {
-    let key_str = key_id.as_ref();
-    let colon_idx =
-        NonZeroU8::new(key_str.find(':').ok_or(Error::MissingServerKeyDelimiter)? as u8)
-            .ok_or(Error::UnknownKeyAlgorithm)?;
-
-    validate_server_key_algorithm(&key_str[..colon_idx.get() as usize])?;
-
-    validate_version(&key_str[colon_idx.get() as usize + 1..])?;
-
+    let colon_idx = ruma_identifiers_validation::server_key_id::validate(key_id.as_ref())?;
     Ok(ServerKeyId { full_id: key_id.into(), colon_idx })
 }
 
 common_impls!(ServerKeyId, try_from, "Key ID with algorithm and version");
 
-fn validate_version(version: &str) -> Result<(), Error> {
-    if version.is_empty() {
-        return Err(Error::MinimumLengthNotSatisfied);
-    } else if !version.chars().all(|c| c.is_alphanumeric() || c == '_') {
-        return Err(Error::InvalidCharacters);
-    }
-
-    Ok(())
-}
-
-fn validate_server_key_algorithm(algorithm: &str) -> Result<(), Error> {
-    match ServerKeyAlgorithm::from_str(algorithm) {
-        Ok(_) => Ok(()),
-        Err(_) => Err(Error::UnknownKeyAlgorithm),
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use std::convert::TryFrom;
@@ -65,10 +40,10 @@ mod tests {
     #[cfg(feature = "serde")]
     use serde_json::{from_value as from_json_value, json, to_value as to_json_value};
 
-    use crate::{error::Error, ServerKeyId};
+    use crate::{Error, ServerKeyId};
 
     #[cfg(feature = "serde")]
-    use crate::key_algorithms::ServerKeyAlgorithm;
+    use ruma_identifiers_validation::key_algorithms::ServerKeyAlgorithm;
 
     #[cfg(feature = "serde")]
     #[test]
diff --git a/ruma-identifiers/src/server_name.rs b/ruma-identifiers/src/server_name.rs
index 58808ba3..fc4e1764 100644
--- a/ruma-identifiers/src/server_name.rs
+++ b/ruma-identifiers/src/server_name.rs
@@ -6,7 +6,9 @@ use std::{
     mem,
 };
 
-use crate::error::Error;
+use ruma_identifiers_validation::server_name::validate;
+
+use crate::Error;
 
 /// A Matrix-spec compliant server name.
 #[repr(transparent)]
@@ -59,51 +61,6 @@ impl From<&ServerName> for Box<ServerName> {
     }
 }
 
-pub(crate) fn validate(server_name: &str) -> Result<(), Error> {
-    use std::net::Ipv6Addr;
-
-    if server_name.is_empty() {
-        return Err(Error::InvalidServerName);
-    }
-
-    let end_of_host = if server_name.starts_with('[') {
-        let end_of_ipv6 = match server_name.find(']') {
-            Some(idx) => idx,
-            None => return Err(Error::InvalidServerName),
-        };
-
-        if server_name[1..end_of_ipv6].parse::<Ipv6Addr>().is_err() {
-            return Err(Error::InvalidServerName);
-        }
-
-        end_of_ipv6 + 1
-    } else {
-        let end_of_host = server_name.find(':').unwrap_or_else(|| server_name.len());
-
-        if server_name[..end_of_host]
-            .bytes()
-            .any(|byte| !(byte.is_ascii_alphanumeric() || byte == b'-' || byte == b'.'))
-        {
-            return Err(Error::InvalidServerName);
-        }
-
-        end_of_host
-    };
-
-    if server_name.len() != end_of_host
-        && (
-            // hostname is followed by something other than ":port"
-            server_name.as_bytes()[end_of_host] != b':'
-            // the remaining characters after ':' are not a valid port
-            || server_name[end_of_host + 1..].parse::<u16>().is_err()
-        )
-    {
-        Err(Error::InvalidServerName)
-    } else {
-        Ok(())
-    }
-}
-
 fn try_from<S>(server_name: S) -> Result<Box<ServerName>, Error>
 where
     S: AsRef<str> + Into<Box<str>>,
@@ -140,7 +97,7 @@ impl<'a> TryFrom<&'a str> for &'a ServerName {
 }
 
 impl TryFrom<&str> for Box<ServerName> {
-    type Error = crate::error::Error;
+    type Error = crate::Error;
 
     fn try_from(s: &str) -> Result<Self, Self::Error> {
         try_from(s)
@@ -148,7 +105,7 @@ impl TryFrom<&str> for Box<ServerName> {
 }
 
 impl TryFrom<String> for Box<ServerName> {
-    type Error = crate::error::Error;
+    type Error = crate::Error;
 
     fn try_from(s: String) -> Result<Self, Self::Error> {
         try_from(s)
diff --git a/ruma-identifiers/src/user_id.rs b/ruma-identifiers/src/user_id.rs
index 9e8847e1..50bb4878 100644
--- a/ruma-identifiers/src/user_id.rs
+++ b/ruma-identifiers/src/user_id.rs
@@ -2,7 +2,7 @@
 
 use std::{convert::TryFrom, num::NonZeroU8};
 
-use crate::{error::Error, parse_id, ServerName};
+use crate::{Error, ServerName};
 
 /// A Matrix user ID.
 ///
@@ -95,41 +95,14 @@ fn try_from<S>(user_id: S) -> Result<UserId, Error>
 where
     S: AsRef<str> + Into<Box<str>>,
 {
-    let user_id_str = user_id.as_ref();
-
-    let colon_idx = parse_id(user_id_str, &['@'])?;
-    let localpart = &user_id_str[1..colon_idx.get() as usize];
-
-    let is_historical = localpart_is_fully_comforming(localpart)?;
-
+    let (colon_idx, is_historical) =
+        ruma_identifiers_validation::user_id::validate(user_id.as_ref())?;
     Ok(UserId { full_id: user_id.into(), colon_idx, is_historical: !is_historical })
 }
 
 common_impls!(UserId, try_from, "a Matrix user ID");
 
-/// Check whether the given user id localpart is valid and fully conforming
-///
-/// Returns an `Err` for invalid user ID localparts, `Ok(false)` for historical user ID localparts
-/// and `Ok(true)` for fully conforming user ID localparts.
-pub fn localpart_is_fully_comforming(localpart: &str) -> Result<bool, Error> {
-    if localpart.is_empty() {
-        return Err(Error::InvalidLocalPart);
-    }
-
-    // See https://matrix.org/docs/spec/appendices#user-identifiers
-    let is_fully_conforming = localpart
-        .bytes()
-        .all(|b| matches!(b, b'0'..=b'9' | b'a'..=b'z' | b'-' | b'.' | b'=' | b'_' | b'/'));
-
-    // If it's not fully conforming, check if it contains characters that are also disallowed
-    // for historical user IDs. If there are, return an error.
-    // See https://matrix.org/docs/spec/appendices#historical-user-ids
-    if !is_fully_conforming && localpart.bytes().any(|b| b < 0x21 || b == b':' || b > 0x7E) {
-        Err(Error::InvalidCharacters)
-    } else {
-        Ok(is_fully_conforming)
-    }
-}
+pub use ruma_identifiers_validation::user_id::localpart_is_fully_comforming;
 
 #[cfg(test)]
 mod tests {
@@ -139,7 +112,7 @@ mod tests {
     use serde_json::{from_str, to_string};
 
     use super::UserId;
-    use crate::{error::Error, ServerName};
+    use crate::{Error, ServerName};
 
     #[test]
     fn valid_user_id_from_str() {