ua

Cross-platform User-Agent generator with best-effort installed browser detection.

This crate detects installed browsers and (when possible) uses their versions to generate realistic User-Agent strings. It supports Windows, macOS, and Linux.

Features

• Platform detection (OS + CPU arch)
• Installed browser detection (best-effort)
• User-Agent generation:
  • Chromium family: Chrome / Edge / Chromium / Brave / Opera
  • Firefox
  • Safari (best-effort only)
• Strictness modes:
  • Real: requires a detected browser version (Safari not supported)
  • BestEffort: falls back to safe defaults

Usage

use ua::{build_user_agent, UaStrictness};

let ua = build_user_agent(UaStrictness::BestEffort)?;
println!("{ua}");
# Ok::<(), ua::AgentError>(())

lib.rs:

ua — User-Agent generation and browser detection utilities.

This crate helps you build realistic User-Agent strings by detecting installed browsers and (when possible) using the detected browser version. It is designed for HTTP clients, automation tools, and apps that need browser-like headers.

Main API

Most users only need:

• build_user_agent to generate a UA string.
• UaStrictness to choose between strict vs resilient behavior.

If you want more control, you can use:

• platform_info to inspect the platform token inputs.
• detect_browsers to list installed browsers.
• choose_best_browser to override selection logic.

What it does

• Detects platform information: OS family and CPU architecture.
• Detects installed browsers (best-effort, OS-specific):
  • Windows: checks common install paths and reads .exe file version metadata.
  • macOS: checks /Applications/*.app and reads Info.plist version metadata.
  • Linux: checks PATH binaries and optionally inspects Flatpak/Snap installs.
• Generates browser-like User-Agent strings for:
  • Chromium family: Chrome / Edge / Chromium / Brave / Opera
  • Firefox
  • Safari (best-effort only)

Strictness

The UaStrictness mode controls how strict UA generation is:

• UaStrictness::Real:
  • Requires a detected browser and a parseable version.
  • Supported for Chromium-family and Firefox.
  • Safari is not supported in Real mode because Safari’s WebKit token mapping is not reliably derivable from the installed version alone.
• UaStrictness::BestEffort:
  • Produces a reasonable UA even when version detection is incomplete.
  • Recommended when you need resilience across varied machines.

Non-goals

• This crate does not attempt full browser fingerprint emulation. For more browser-like behavior, also consider sending UA-CH and Sec-Fetch headers.

Example

use ua::{build_user_agent, UaStrictness};
let ua = build_user_agent(UaStrictness::BestEffort)?;
println!("{ua}");

Notes on privacy and ethics

Browser-like headers can be used to reduce false blocks in legitimate automation, but also can be used for deceptive fingerprinting. Use responsibly and comply with applicable terms and policies.