diff --git a/bff-cli/src/diff.rs b/bff-cli/src/diff.rs
new file mode 100644
index 0000000..a259e68
--- /dev/null
+++ b/bff-cli/src/diff.rs
@@ -0,0 +1,173 @@
+use std::collections::BTreeMap;
+use std::fs::File;
+use std::io::Write;
+use std::path::{Path, PathBuf};
+
+use bff::BufReader;
+use bff::bigfile::BigFile;
+use bff::bigfile::resource::Resource;
+use bff::names::NameContext;
+
+use crate::error::BffCliResult;
+use crate::extract::{read_bigfile, read_bigfile_names};
+
+struct ResolvedResource<'a> {
+    link_name: Option<String>,
+    resource: &'a Resource,
+}
+
+fn read_name_file(name_path: &Path, name_context: &NameContext) -> BffCliResult<()> {
+    let f = File::open(name_path)?;
+    let mut reader = BufReader::new(f);
+    name_context.read(&mut reader)?;
+    Ok(())
+}
+
+fn load_bigfile(
+    bigfile_path: &Path,
+    name_path: &Option<PathBuf>,
+) -> BffCliResult<(BigFile, NameContext)> {
+    let name_context = NameContext::default();
+    read_bigfile_names(bigfile_path, &name_context)?;
+    if let Some(name_path) = name_path {
+        read_name_file(name_path, &name_context)?;
+    }
+    let bigfile = read_bigfile(bigfile_path, &None, &None, &name_context)?;
+    Ok((bigfile, name_context))
+}
+
+fn resolve_resources<'a>(
+    bigfile: &'a BigFile,
+    name_context: &NameContext,
+    side: &'static str,
+) -> BffCliResult<BTreeMap<String, ResolvedResource<'a>>> {
+    let mut resources = BTreeMap::new();
+
+    for resource in bigfile.resources.values() {
+        let resource_name = resource.name.with_context(name_context).to_string();
+        let class_name = resource.class_name.with_context(name_context).to_string();
+        let full_name = format!("{resource_name}.{class_name}");
+        let resolved_resource = ResolvedResource {
+            link_name: resource
+                .link_name
+                .as_ref()
+                .map(|name| name.with_context(name_context).to_string()),
+            resource,
+        };
+
+        assert!(
+            resources
+                .insert(full_name.clone(), resolved_resource)
+                .is_none(),
+            "duplicate resolved resource name {full_name} in {side}"
+        );
+    }
+
+    Ok(resources)
+}
+
+fn display_link_name(link_name: &Option<String>) -> &str {
+    link_name.as_deref().unwrap_or("<none>")
+}
+
+fn describe_data_change(old_resource: &Resource, new_resource: &Resource) -> String {
+    let old_size = old_resource.size();
+    let new_size = new_resource.size();
+
+    if old_size == new_size {
+        format!("data changed ({old_size} bytes)")
+    } else {
+        format!("data: {old_size} -> {new_size} bytes")
+    }
+}
+
+fn describe_changes(old_resource: &ResolvedResource<'_>, new_resource: &ResolvedResource<'_>) -> Vec<String> {
+    let mut changes = Vec::new();
+
+    if old_resource.link_name != new_resource.link_name {
+        changes.push(format!(
+            "link: {} -> {}",
+            display_link_name(&old_resource.link_name),
+            display_link_name(&new_resource.link_name)
+        ));
+    }
+
+    if old_resource.resource.data != new_resource.resource.data {
+        changes.push(describe_data_change(
+            old_resource.resource,
+            new_resource.resource,
+        ));
+    }
+
+    changes
+}
+
+pub fn diff(
+    old_bigfile_path: &Path,
+    new_bigfile_path: &Path,
+    old_name_path: &Option<PathBuf>,
+    new_name_path: &Option<PathBuf>,
+) -> BffCliResult<()> {
+    let (old_bigfile, old_name_context) = load_bigfile(old_bigfile_path, old_name_path)?;
+    let (new_bigfile, new_name_context) = load_bigfile(new_bigfile_path, new_name_path)?;
+
+    let old_resources = resolve_resources(&old_bigfile, &old_name_context, "old BigFile")?;
+    let new_resources = resolve_resources(&new_bigfile, &new_name_context, "new BigFile")?;
+
+    let added = new_resources
+        .iter()
+        .filter(|(name, _)| !old_resources.contains_key(*name))
+        .collect::<Vec<_>>();
+    let removed = old_resources
+        .iter()
+        .filter(|(name, _)| !new_resources.contains_key(*name))
+        .collect::<Vec<_>>();
+    let changed = old_resources
+        .iter()
+        .filter_map(|(name, old_resource)| {
+            let new_resource = new_resources.get(name)?;
+            let changes = describe_changes(old_resource, new_resource);
+            (!changes.is_empty()).then_some((name, old_resource, new_resource, changes))
+        })
+        .collect::<Vec<_>>();
+
+    let mut stdout = std::io::stdout().lock();
+
+    if added.is_empty() && removed.is_empty() && changed.is_empty() {
+        writeln!(stdout, "No differences found.")?;
+        return Ok(());
+    }
+
+    let mut wrote_section = false;
+
+    if !added.is_empty() {
+        writeln!(stdout, "Added:")?;
+        for (name, _) in &added {
+            writeln!(stdout, "  {name}")?;
+        }
+        wrote_section = true;
+    }
+
+    if !removed.is_empty() {
+        if wrote_section {
+            writeln!(stdout)?;
+        }
+        writeln!(stdout, "Removed:")?;
+        for (name, _) in &removed {
+            writeln!(stdout, "  {name}")?;
+        }
+        wrote_section = true;
+    }
+
+    if !changed.is_empty() {
+        if wrote_section {
+            writeln!(stdout)?;
+        }
+        writeln!(stdout, "Changed:")?;
+        for (name, _, _, changes) in &changed {
+            writeln!(stdout, "  {name} ({})", changes.join(", "))?;
+        }
+    }
+
+    Ok(())
+}
diff --git a/bff-cli/src/main.rs b/bff-cli/src/main.rs
index 6c0814d..2ac00ec 100644
--- a/bff-cli/src/main.rs
+++ b/bff-cli/src/main.rs
@@ -15,6 +15,7 @@ mod crc;
 mod create;
 mod create_resource;
 mod csc;
+mod diff;
 mod dump_json_schema;
 mod error;
 mod extract;
@@ -100,6 +101,14 @@ enum Commands {
         #[arg(long)]
         out_reference_graph: Option<PathBuf>,
     },
+    Diff {
+        old_bigfile: PathBuf,
+        new_bigfile: PathBuf,
+        #[arg(long)]
+        old_names: Option<PathBuf>,
+        #[arg(long)]
+        new_names: Option<PathBuf>,
+    },
     Names {
         bigfile: Option<PathBuf>,
         #[clap(value_enum)]
@@ -293,6 +302,12 @@ fn main() -> BffCliResult<()> {
             in_names,
             out_reference_graph: out_dependencies,
         } => info::info(bigfile, in_names, out_dependencies, &name_context),
+        Commands::Diff {
+            old_bigfile,
+            new_bigfile,
+            old_names,
+            new_names,
+        } => diff::diff(old_bigfile, new_bigfile, old_names, new_names),
         Commands::Names {
             bigfile,
             wordlist,