Microsoft to open source Chakra, the JavaScript heart of its Edge browser
Source will be available from January, and open to community contributions. — At JSConf in Florida today, Microsoft announced that it is open sourcing Chakra, the JavaScript engine used in its Edge and Internet Explorer browsers.
Context & Ripple Effects
2015 was the year Microsoft rebuilt its browser story from scratch: the EdgeHTML rendering engine debuted with the Spartan project, and by May Edge had shipped extensions support and asm.js performance while dropping ActiveX. The Chakra announcement at JSConf extends that reset below the rendering layer — the JavaScript heart shared by Edge and Internet Explorer goes open source, with code available from January.
First-order effects
- Developers gain visibility into and contribution rights over the engine powering Edge and Internet Explorer — a reversal for a component Microsoft had kept closed through two decades of IE.
- The January source drop sets up a standalone life for the engine beyond Microsoft's own browsers, which is exactly what materializes weeks later when ChakraCore ships as a separate open-source project.
Second-order effects
- Google's V8 and Mozilla's SpiderMonkey now face a third major engine competing for embedders on openness as well as speed, pressuring the whole engine layer to court non-browser hosts.
- An independently governable ChakraCore gives tooling and runtime projects outside Microsoft an alternative to forking V8, shifting some engine choice away from whichever browser ships it.
Third-order effects
- Openness alone didn't secure the engine's future: three years later Microsoft put Edge on Chromium, swapping Chakra for V8 while bringing Chrome extension compatibility to Edge users — evidence that engine economics favor consolidation around the largest shared codebase.
- If that pattern holds, browser engines trend toward a small set of jointly maintained open cores, with individual vendors contributing rather than maintaining proprietary forks — the trajectory Microsoft's own framing of its Chromium investment points to.
The trend: Browser engines are converging on shared open-source cores, with vendor-specific engines like Chakra becoming either community projects or casualties of consolidation.