&gt; As far as I remember, Chrome has used the STL earlier. But I looked now and I see this:<p>The WTF (Web Template Framework) is actually inherited from WebKit and used in the core rendering engine. I&#x27;m not sure how widely it&#x27;s used in the Google parts of Chromium.<p>&gt; Gecko also seem to have a lot of custom stuff<p>That&#x27;s the old XPCOM stuff. While those string types continue to get a lot of use, the closest analogue to the STL is MFBT: <a href="https:&#x2F;&#x2F;github.com&#x2F;mozilla&#x2F;gecko-dev&#x2F;tree&#x2F;master&#x2F;mfbt" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;mozilla&#x2F;gecko-dev&#x2F;tree&#x2F;master&#x2F;mfbt</a>