Parsers

browserget talks to four different upstream APIs to resolve browser and driver versions. Each API has a different format, so browserget uses dedicated parsers that transform raw responses into ResolvedVersion objects.

Upstream APIs

Chrome for Testing (CfT)

Chrome and ChromeDriver versions are resolved from the Chrome for Testing JSON API.

• URL: https://googlechromelabs.github.io/chrome-for-testing/known-good-versions-with-downloads.json
• Format: JSON
• Structure: A versions array, each entry contains a version string and a downloads object with platform-specific URLs for chrome and chromedriver.
• Checksums: Provided as checksum fields in the download entries.

The parser (parsers/cft.py) filters versions by target (chrome or chromedriver) and platform string (e.g. win64, linux64, mac-arm64). Versions are sorted in descending order so the first match is the latest.

Firefox FTP

Firefox versions are scraped from the Mozilla FTP directory listing.

• URL: https://ftp.mozilla.org/pub/firefox/releases/
• Format: HTML directory listing
• Structure: The page contains <a> tags with version directory names (e.g. 131.0/, 130.0/, 128.0esr/).
• Checksums: Available via separate checksum files in each version directory.

The parser (parsers/firefox.py) uses regex to extract version strings from the HTML, handles esr (Extended Support Release) variants, and constructs download and checksum URLs based on the version and platform.

Edge Updates API

Edge browser versions are resolved from the Microsoft Edge Updates API.

• URL: https://edgeupdates.microsoft.com/api/products
• Format: JSON
• Structure: An array of products, each with a Product name and a Releases list. Each release contains Platform, Architecture, ProductVersion, and an Artifacts array. Each artifact has Location, Hash, and HashAlgorithm fields.
• Checksums: Provided as Hash and HashAlgorithm fields in the artifact entries.

The parser (parsers/edge.py) only supports the Stable product and the edge target. It filters by the mapped Platform and Architecture and returns the first artifact for each matching release.

EdgeDriver CDN

EdgeDriver is not available from the Edge Updates API. It is distributed from a separate CDN:

• Latest version URL: https://msedgedriver.microsoft.com/LATEST_STABLE
• Download URL: https://msedgedriver.microsoft.com/{version}/edgedriver_{platform}.zip
• Format: Zip archive, no checksums published.

GeckoDriver GitHub releases

GeckoDriver versions are resolved from the GitHub Releases API.

• URL: https://api.github.com/repos/mozilla/geckodriver/releases
• Format: JSON
• Structure: An array of release objects, each with a tag_name (e.g. v0.35.0) and an assets array containing download URLs.
• Checksums: Not provided by GitHub releases. GeckoDriver downloads skip checksum verification.

The parser (parsers/geckodriver.py) maps GitHub asset names to internal platform strings (e.g. geckodriver-v0.35.0-win64.zip to win64). The v prefix in tag_name is stripped for version comparison.

Platform mapping

browserget detects the current OS and architecture, then maps to the platform string expected by each upstream API:

Internal platform	CfT	Firefox FTP	Edge API	GeckoDriver
win64	win64	win64/	win64	win64.zip
win32	win32	win32/	win64	win32.zip
linux64	linux64	linux-x86_64/	linux64	linux64.tar.gz
linux-arm64	linux64	linux-aarch64/	linux64	linux-aarch64.tar.gz
mac-arm64	mac-arm64	mac/	mac-arm64	macos-aarch64.tar.gz
mac-x64	mac-x64	mac/	mac-x64	macos.tar.gz

The map_platform() function in platform.py handles this translation.

Version resolution

browserget supports three version input modes:

Mode	Example	Behavior
Latest	(no --version)	Returns the most recent version from the API
Exact	131.0.6778.87	Finds the exact matching version
Milestone	131	Returns the latest patch within the milestone

Resolution logic

parse input
  │
  ├─ no version → return latest (first in sorted descending list)
  │
  ├─ exact version (4 parts: X.Y.Z.W)
  │   └─ find exact match in version list
  │       └─ not found → VersionNotFoundError
  │
  └─ milestone (1 part: X)
      └─ filter versions starting with "X."
          └─ return first (latest patch)
              └─ none found → VersionNotFoundError

GeckoDriver does not match Firefox

Unlike ChromeDriver, GeckoDriver does not version-match with Firefox. The --for firefox flag for geckodriver simply installs the latest GeckoDriver regardless of the Firefox version. This is by design — GeckoDriver maintains its own release cadence independent of Firefox versions.