Agent Shift - User Agent Switch by kyojin

Agent Shift gives you control over the browser identity Firefox presents to websites. Choose a preset, create your own user agent, or assign different identities to individual sites.

Features include:

• 87 presets covering Chrome, Firefox, Edge, and Safari across desktop and mobile platforms.
• Per-site rules with optional subdomain matching and native Firefox exceptions.
• Custom profiles with user-agent previews, editing, duplication, and copy controls.
• Quick filtering by browser, version, device, and favorites.
• One-click pause to return to your native Firefox identity.
• Dark, light, and system themes in a compact popup, with an optional larger workspace.
• Local backup and restore through JSON import and export.

Built with a Rust/WebAssembly core. Settings stay on your device, with no accounts, tracking, or telemetry.

Agent Shift is a compatibility and testing tool. Changing your user agent does not change Firefox’s underlying engine, hide your IP address, or make you anonymous. Presets use fixed browser versions, and some changes require reloading the website.