diff --git a/Cargo.lock b/Cargo.lock
index 805ccff..ec443ba 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -17,6 +17,15 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
 
+[[package]]
+name = "aho-corasick"
+version = "0.7.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e37cfd5e7657ada45f742d6e99ca5788580b5c529dc78faf11ece6dc702656f"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "ansi_term"
 version = "0.12.1"
@@ -1424,6 +1433,8 @@ version = "1.5.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d07a8629359eb56f1e2fb1652bb04212c072a87ba68546a04065d525673ac461"
 dependencies = [
+ "aho-corasick",
+ "memchr",
  "regex-syntax",
 ]
 
@@ -1974,6 +1985,7 @@ dependencies = [
  "miette",
  "notify",
  "once_cell",
+ "regex",
  "thiserror",
  "tokio",
  "tracing",
diff --git a/lib/Cargo.toml b/lib/Cargo.toml
index bde3e98..601d4fa 100644
--- a/lib/Cargo.toml
+++ b/lib/Cargo.toml
@@ -24,6 +24,7 @@ futures = "0.3.16"
 miette = "1.0.0-beta.1"
 notify = "5.0.0-pre.12"
 once_cell = "1.8.0"
+regex = "1.5.4"
 thiserror = "1.0.26"
 tracing = "0.1.26"
 
diff --git a/lib/src/command/supervisor.rs b/lib/src/command/supervisor.rs
index 23a8ca4..805fc46 100644
--- a/lib/src/command/supervisor.rs
+++ b/lib/src/command/supervisor.rs
@@ -17,7 +17,7 @@ use tracing::{debug, error, trace, warn};
 
 use crate::{
 	error::RuntimeError,
-	event::{Event, Tag, Source},
+	event::{Event, Source, Tag},
 };
 
 use super::Process;
diff --git a/lib/src/filter.rs b/lib/src/filter.rs
new file mode 100644
index 0000000..e83bc73
--- /dev/null
+++ b/lib/src/filter.rs
@@ -0,0 +1,45 @@
+use std::{collections::HashSet, path::PathBuf};
+
+use regex::Regex;
+
+use crate::event::Tag;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Filter {
+	pub in_path: Option<PathBuf>,
+	pub on: Tag,
+	pub op: Op,
+	pub pat: Pattern,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Op {
+	Equal,
+	NotEqual,
+	Regex,
+	Glob,
+	Includes,
+	Excludes,
+	InSet,
+	OutSet,
+}
+
+#[derive(Debug, Clone)]
+pub enum Pattern {
+	Exact(String),
+	Regex(Regex),
+	Set(HashSet<String>),
+}
+
+impl PartialEq<Self> for Pattern {
+	fn eq(&self, other: &Self) -> bool {
+		match (self, other) {
+			(Self::Exact(l), Self::Exact(r)) => l == r,
+			(Self::Regex(l), Self::Regex(r)) => l.as_str() == r.as_str(),
+			(Self::Set(l), Self::Set(r)) => l == r,
+			_ => false,
+		}
+	}
+}
+
+impl Eq for Pattern {}
diff --git a/lib/src/fs.rs b/lib/src/fs.rs
index ae3250a..83eef85 100644
--- a/lib/src/fs.rs
+++ b/lib/src/fs.rs
@@ -14,7 +14,7 @@ use tracing::{debug, error, trace};
 
 use crate::{
 	error::{CriticalError, RuntimeError},
-	event::{Event, Tag, Source},
+	event::{Event, Source, Tag},
 };
 
 /// What kind of filesystem watcher to use.
@@ -249,10 +249,7 @@ fn process_event(
 		metadata.insert("notify-backend".to_string(), vec![src.to_string()]);
 	}
 
-	let ev = Event {
-		tags,
-		metadata,
-	};
+	let ev = Event { tags, metadata };
 
 	trace!(event = ?ev, "processed notify event into watchexec event");
 	n_events
diff --git a/lib/src/lib.rs b/lib/src/lib.rs
index 4f916f2..4319a9a 100644
--- a/lib/src/lib.rs
+++ b/lib/src/lib.rs
@@ -90,6 +90,7 @@ pub mod action;
 pub mod command;
 pub mod error;
 pub mod event;
+pub mod filter;
 pub mod fs;
 pub mod signal;
 
diff --git a/lib/src/signal.rs b/lib/src/signal.rs
index a04227a..ec62504 100644
--- a/lib/src/signal.rs
+++ b/lib/src/signal.rs
@@ -5,7 +5,7 @@ use tracing::{debug, trace};
 
 use crate::{
 	error::{CriticalError, RuntimeError},
-	event::{Event, Tag, Source},
+	event::{Event, Source, Tag},
 };
 
 /// A notification sent to the main (watchexec) process.