Engines/gecko
Mozilla

Gecko

Mozilla’s layout engine behind Firefox and Firefox-derived browsers. Identifies itself with a Gecko/… rv:… token (and usually Firefox/…).

Jan 2015
first seen in our archive
143K
distinct User-Agents
11M+
requests seen

Official: developer.mozilla.org/en-US/docs/Mozilla/Gecko·Vendor: Mozilla

Browsers on Gecko

Directory browsers that primarily ship with this layout engine.

Most parsed browsers →

Parse it

Send the User-Agent to the API, device, OS, browser, and bot detection come back in one response. Paid deep returns the engine as `Gecko` when the string matches.

curl -s "https://api.parseapi.com/useragent?deep=true" \
  -H "User-Agent: mozilla/5.0 (windows nt 6.1; rv:52.0) gecko/20100101 firefox/52.0" \
  -H "X-Api-Key: $PARSEAPI_KEY"

# deep.engine → { "name": "Gecko", "version": … }
Create a free keyUseragent API

Example User-Agents

Real strings from our archive that resolve to Gecko. Each opens a full breakdown.