Firefox 78 for developers

This article provides information about the changes in Firefox 78 that will affect developers. Firefox 78 was released on June 30, 2020.

See also New in Firefox 78: DevTools improvements, new regex engine, and abundant web platform updates on Mozilla hacks.

Changes for web developers

Developer Tools


Network Monitor

Other tools

  • The Accessibility inspector is out of beta. You can use it to check for various accessibility issues on your site. (Firefox bug 1602075)
  • Uncaught promise errors now provide all details in the Console, including their name and stack. (Firefox bug 1636590)





Service workers


  • Wasm Multi-value is now supported, meaning that WebAssembly functions can now return multiple values, and instruction sequences can consume and produce multiple stack values (Firefox bug 1628321).
  • WebAssembly now supports import and export of 64-bit integer function parameters (i64) using BigInt from JavaScript (Firefox bug 1608770).

TLS 1.0 and 1.1 removal

Changes for add-on developers

Older versions