diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 8e05fd9..12f8fc9 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -32,8 +32,26 @@ jobs:
       - name: Install ${{ matrix.rust }} Rust
         run: rustup default ${{ matrix.rust }}
 
-      - name: Build and test
-        run: cargo test
+        # Verify that features work by themselves
+        # Features should not interfere with each other
+        # Should only need to check 0, 1, and (all) 3 features enabled
+
+        # Use if statement to invert exit code: this should fail
+      - name: Check failure to build with no features
+        run: if cargo check --no-default-features; then false; else true; fi
+        shell: bash
+
+      - name: Build and test with markdown_deps_updated feature
+        run: cargo test --no-default-features --features markdown_deps_updated
+
+      - name: Build and test with html_root_url_updated feature
+        run: cargo test --no-default-features --features html_root_url_updated
+
+      - name: Build and test with contains_regex feature
+        run: cargo test --no-default-features --features contains_regex
+
+      - name: Build and test with all features
+        run: cargo test --all-features
 
   build-documentation:
     name: Build documentation
diff --git a/Cargo.toml b/Cargo.toml
index 5e4eed1..47c80d5 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,14 +11,20 @@ categories = ["development-tools", "rust-patterns"]
 license = "MIT"
 edition = "2018"
 
+[features]
+default = ["markdown_deps_updated", "html_root_url_updated", "contains_regex"]
+markdown_deps_updated = ["pulldown-cmark", "semver-parser", "toml"]
+html_root_url_updated = ["url", "semver-parser", "syn", "proc-macro2"]
+contains_regex = ["regex"]
+
 [dependencies]
-pulldown-cmark = { version = "0.8", default-features = false }
-semver-parser = "0.9"
-syn = { version = "1.0", features = ["full"] }
-proc-macro2 = { version = "1.0", features = ["span-locations"] }
-toml = "0.5"
-url = "2.0"
-regex = { version = "1.3", default-features = false, features = ["std", "unicode"] }
+pulldown-cmark = { version = "0.8", default-features = false, optional = true }
+semver-parser = { version = "0.9", optional = true }
+syn = { version = "1.0", default-features = false, features = ["parsing", "printing", "full"], optional = true }
+proc-macro2 = { version = "1.0", default-features = false, features = ["span-locations"], optional = true }
+toml = { version = "0.5", optional = true }
+url = { version = "2.0", optional = true }
+regex = { version = "1.3", default-features = false, features = ["std", "unicode"], optional = true }
 
 [dev-dependencies]
 tempfile = "3.1"
diff --git a/src/contains_regex.rs b/src/contains_regex.rs
index 16e574a..cee0e13 100644
--- a/src/contains_regex.rs
+++ b/src/contains_regex.rs
@@ -1,3 +1,4 @@
+#![cfg(feature = "contains_regex")]
 use regex::{escape, Regex};
 
 use crate::helpers::{read_file, Result};
diff --git a/src/helpers.rs b/src/helpers.rs
index 92cf699..1bd7b3a 100644
--- a/src/helpers.rs
+++ b/src/helpers.rs
@@ -1,18 +1,13 @@
-use std::fmt::Display;
-use std::fs::File;
-use std::io::{self, Read};
-use std::result;
-
-use semver_parser::range::{Op, VersionReq};
-use semver_parser::version::Version;
+// Imports are inside the function bodies to scope them in a cfg block.
 
 /// The common result type, our errors will be simple strings.
-pub type Result<T> = result::Result<T, String>;
+pub type Result<T> = std::result::Result<T, String>;
 
+#[cfg(any(feature = "html_root_url_updated", feature = "markdown_deps_updated"))]
 fn join<T>(iter: T, sep: &str) -> String
 where
     T: IntoIterator,
-    T::Item: Display,
+    T::Item: std::fmt::Display,
 {
     let mut buf = String::new();
     let mut iter = iter.into_iter();
@@ -33,20 +28,26 @@ where
 /// Return all data from `path`. Line boundaries are normalized from
 /// "\r\n" to "\n" to make sure "^" and "$" will match them. See
 /// https://github.com/rust-lang/regex/issues/244 for details.
-pub fn read_file(path: &str) -> io::Result<String> {
-    let mut file = File::open(path)?;
+pub fn read_file(path: &str) -> std::io::Result<String> {
+    use std::io::Read;
+
+    let mut file = std::fs::File::open(path)?;
     let mut buf = String::new();
     file.read_to_string(&mut buf)?;
     Ok(buf.replace("\r\n", "\n"))
 }
 
 /// Indent every line in text by four spaces.
+#[cfg(any(feature = "html_root_url_updated", feature = "markdown_deps_updated"))]
 pub fn indent(text: &str) -> String {
     join(text.lines().map(|line| String::from("    ") + line), "\n")
 }
 
 /// Verify that the version range request matches the given version.
-pub fn version_matches_request(version: &Version, request: &VersionReq) -> Result<()> {
+#[cfg(any(feature = "html_root_url_updated", feature = "markdown_deps_updated"))]
+pub fn version_matches_request(version: &semver_parser::version::Version,
+        request: &semver_parser::range::VersionReq) -> Result<()> {
+    use semver_parser::range::Op;
     if request.predicates.len() != 1 {
         // Can only handle simple dependencies
         return Ok(());
@@ -93,11 +94,15 @@ pub fn version_matches_request(version: &Version, request: &VersionReq) -> Resul
 
 #[cfg(test)]
 mod tests {
+    #[cfg(any(feature = "html_root_url_updated", feature = "markdown_deps_updated"))]
     use semver_parser::range::parse as parse_request;
+    #[cfg(any(feature = "html_root_url_updated", feature = "markdown_deps_updated"))]
     use semver_parser::version::parse as parse_version;
 
+    #[cfg(any(feature = "html_root_url_updated", feature = "markdown_deps_updated"))]
     use super::*;
 
+    #[cfg(any(feature = "html_root_url_updated", feature = "markdown_deps_updated"))]
     mod test_version_matches_request {
         use super::*;
 
diff --git a/src/html_root_url.rs b/src/html_root_url.rs
index d093f86..5369c99 100644
--- a/src/html_root_url.rs
+++ b/src/html_root_url.rs
@@ -1,3 +1,4 @@
+#![cfg(feature = "html_root_url_updated")]
 use semver_parser::range::parse as parse_request;
 use semver_parser::version::parse as parse_version;
 use semver_parser::version::Version;
diff --git a/src/lib.rs b/src/lib.rs
index 42a8909..472cc6e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,8 @@
 //! `version-sync` provides macros for keeping version numbers in sync
 //! with your crate version.
 //!
+//! # Library Overview
+//!
 //! When making a release of a Rust project, you typically need to
 //! adjust some version numbers in your code and documentation. This
 //! crate gives you macros that covers some typical cases where
@@ -10,10 +12,14 @@
 //!   dependency on your crate. See [`assert_markdown_deps_updated`].
 //!
 //! * A `Changelog.md` file that should at least mention the current
-//!   version. See [`assert_contains_regex`].
+//!   version, gated behind the "regex_version" feature.
+//!   See [`assert_contains_regex`].
 //!
 //! * The [`html_root_url`] attribute that tells other crates where to
-//!   find your documentation. See [`assert_html_root_url_updated`].
+//!   find your documentation, gated behind the "html_root_url" feature.
+//!   See [`assert_html_root_url_updated`].
+//!
+//! The macros are gated behind individual features, as detailed below.
 //!
 //! A typical configuration will use an integration test to verify
 //! that all version numbers are in sync. Create a
@@ -22,18 +28,22 @@
 //! ```rust
 //! #[test]
 //! # fn fake_hidden_test_case_1() {}
+//! # #[cfg(feature = "markdown_deps_updated")]
 //! fn test_readme_deps() {
 //!     version_sync::assert_markdown_deps_updated!("README.md");
 //! }
 //!
 //! #[test]
 //! # fn fake_hidden_test_case_2() {}
+//! # #[cfg(feature = "html_root_url_updated")]
 //! fn test_html_root_url() {
 //!     version_sync::assert_html_root_url_updated!("src/lib.rs");
 //! }
 //!
 //! # fn main() {
+//! #     #[cfg(feature = "markdown_deps_updated")]
 //! #     test_readme_deps();
+//! #     #[cfg(feature = "html_root_url_updated")]
 //! #     test_html_root_url();
 //! # }
 //! ```
@@ -41,6 +51,16 @@
 //! When you run `cargo test`, your version numbers will be
 //! automatically checked.
 //!
+//! # Cargo Features
+//!
+//! Each of the macros above are gated behind a feature:
+//!
+//! * `markdown_deps_updated` enables [`assert_markdown_deps_updated`].
+//! * `html_root_url_updated` enables [`assert_html_root_url_updated`].
+//! * `contains_regex` enables [`assert_contains_regex`].
+//!
+//! All of these features are enabled by default.
+//!
 //! [`html_root_url`]: https://rust-lang-nursery.github.io/api-guidelines/documentation.html#crate-sets-html_root_url-attribute-c-html-root
 //! [`assert_markdown_deps_updated`]: macro.assert_markdown_deps_updated.html
 //! [`assert_html_root_url_updated`]: macro.assert_html_root_url_updated.html
@@ -54,8 +74,16 @@ mod helpers;
 mod html_root_url;
 mod markdown_deps;
 
+// Ensure that at least one feature is enabled
+#[cfg(not(any(feature = "contains_regex", feature = "html_root_url_updated",
+    feature = "markdown_deps_updated")))]
+std::compile_error!("Please select at least one feature.");
+
+#[cfg(feature = "contains_regex")]
 pub use crate::contains_regex::check_contains_regex;
+#[cfg(feature = "html_root_url_updated")]
 pub use crate::html_root_url::check_html_root_url;
+#[cfg(feature = "markdown_deps_updated")]
 pub use crate::markdown_deps::check_markdown_deps;
 
 /// Assert that dependencies on the current package are up to date.
@@ -68,6 +96,8 @@ pub use crate::markdown_deps::check_markdown_deps;
 /// variables are automatically set by Cargo when compiling your
 /// crate.
 ///
+/// This macro is enabled by the `markdown_deps_updated` feature.
+///
 /// # Usage
 ///
 /// The typical way to use this macro is from an integration test:
@@ -95,6 +125,7 @@ pub use crate::markdown_deps::check_markdown_deps;
 ///
 /// [`check_markdown_deps`]: fn.check_markdown_deps.html
 #[macro_export]
+#[cfg(feature = "markdown_deps_updated")]
 macro_rules! assert_markdown_deps_updated {
     ($path:expr) => {
         let pkg_name = env!("CARGO_PKG_NAME");
@@ -119,6 +150,8 @@ macro_rules! assert_markdown_deps_updated {
 /// `$CARGO_PKG_VERSION`. These environment variables are
 /// automatically set by Cargo when compiling your crate.
 ///
+/// This macro is enabled by the `html_root_url_updated` feature.
+///
 /// # Usage
 ///
 /// The typical way to use this macro is from an integration test:
@@ -147,6 +180,7 @@ macro_rules! assert_markdown_deps_updated {
 /// [api-guidelines]: https://rust-lang-nursery.github.io/api-guidelines/documentation.html#crate-sets-html_root_url-attribute-c-html-root
 /// [`check_html_root_url`]: fn.check_html_root_url.html
 #[macro_export]
+#[cfg(feature = "html_root_url_updated")]
 macro_rules! assert_html_root_url_updated {
     ($path:expr) => {
         let pkg_name = env!("CARGO_PKG_NAME");
@@ -170,6 +204,8 @@ macro_rules! assert_html_root_url_updated {
 /// environment variables. These environment variables are
 /// automatically set by Cargo when compiling your crate.
 ///
+/// This macro is enabled by the `contains_regex` feature.
+///
 /// # Usage
 ///
 /// The typical way to use this macro is from an integration test:
@@ -210,6 +246,7 @@ macro_rules! assert_html_root_url_updated {
 ///
 /// [`check_contains_regex`]: fn.check_contains_regex.html
 #[macro_export]
+#[cfg(feature = "contains_regex")]
 macro_rules! assert_contains_regex {
     ($path:expr, $format:expr) => {
         let pkg_name = env!("CARGO_PKG_NAME");
diff --git a/src/markdown_deps.rs b/src/markdown_deps.rs
index e2b0acc..c36dc2d 100644
--- a/src/markdown_deps.rs
+++ b/src/markdown_deps.rs
@@ -1,3 +1,4 @@
+#![cfg(feature = "markdown_deps_updated")]
 use pulldown_cmark::{CodeBlockKind::Fenced, Event, Parser, Tag};
 use semver_parser::range::parse as parse_request;
 use semver_parser::range::VersionReq;
diff --git a/tests/version-numbers.rs b/tests/version-numbers.rs
index 5a9064a..277ad64 100644
--- a/tests/version-numbers.rs
+++ b/tests/version-numbers.rs
@@ -1,9 +1,11 @@
 #[test]
+#[cfg(feature = "markdown_deps_updated")]
 fn test_readme_deps() {
     version_sync::assert_markdown_deps_updated!("README.md");
 }
 
 #[test]
+#[cfg(feature = "contains_regex")]
 fn test_readme_changelog() {
     version_sync::assert_contains_regex!(
         "README.md",
@@ -12,6 +14,7 @@ fn test_readme_changelog() {
 }
 
 #[test]
+#[cfg(feature = "html_root_url_updated")]
 fn test_html_root_url() {
     version_sync::assert_html_root_url_updated!("src/lib.rs");
 }