Firefox Developer Version



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

Adobe acrobat reader version 5.0 for mac. The Firefox Developer Edition is a modified version of Firefox, specifically designed for web developers. It uses a separate profile than the regular version of Firefox. Meaning you can have both Firefox or F-beta, installed next to the developer edition. Note that your F.D.E. Program for running directx on mac. Will be a completely UN-customized browser.

Firefox was created by Dave Hyatt and Blake Ross as an experimental branch of the Mozilla browser, first released as Firefox 1.0 on November 9, 2004. Starting with version 5.0, a rapid release cycle was put into effect, resulting in a new major version release every six weeks.This was gradually accelerated further in late 2019, so that new major releases occur on four-week cycles starting in 2020. Firefox Browser Developer Edition The browser made for developers All the latest developer tools in beta, plus experimental features like the Multi-line Console Editor and WebSocket Inspector. A separate profile and path so you can easily run it alongside Release or Beta Firefox.

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

Debugger

  • You can now change the URL accessed by the remote device from the about:debugging panel. (bug 1617237)
  • The Disable JavaScript menu item in the Debugger now only affects the current tab, and is reset when the Developer Tools are closed. (bug 1640318)
  • Logpoints can map variable names in source-mapped code back to their original names, if you enable Maps in the Scopes pane. (bug 1536857)
Firefox developer browser

Network Monitor

  • In the Network Monitor, you can now resize the columns of the request list by dragging the column borders anywhere in the table. (bug 1618409)
  • The request details panel in the Network Monitor has some UX improvements. (bug 1631302, bug 1631295)
  • If a request was blocked, the request list now shows the reason, such as an add-on, CSP, CORS, or Enhanced Tracking Protection. (bug 1555057, bug 1445637, bug 1556451)
Firefox

Other tools

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

CSS

  • The :is() and :where() pseudo-classes are now enabled by default (bug 1632646).
  • The :read-only and :read-write pseudo-classes are now supported without prefixes (bug 312971).
    • In addition, :read-write styles are no longer applied to disabled <input> and <textarea> elements, which was a violation of the HTML spec (bug 888884).

JavaScript

Developer

Mozilla Firefox Developer Version

  • The Intl.ListFormat API is now supported (bug 1589095).
  • The Intl.NumberFormat() constructor has been extended to support new options specified in the Intl.NumberFormat Unified API Proposal (bug 1633836). This includes among other things:
    • Unit, currency and sign display formatting
  • The RegExp engine has been updated and now supports all new features introduced in ECMAScript 2018:
    • Lookbehind assertions (bug 1225665)
    • RegExp.prototype.dotAll (bug 1361856)
    • Unicode property escapes (bug 1361876)
    • Named capture groups (bug 1362154)
  • Due to a WebIDL spec change in mid-2020, we've added a Symbol.toStringTag property to all DOM prototype objects (bug 1277799).
  • The garbage collection of WeakMap objects has been improved. WeakMaps are now marked incrementally (bug 1167452).

APIs

DOM

Firefox Developer Version Download

  • The ParentNode.replaceChildren() method has been implemented (bug 1626015).

Service workers

  • Extended Support Releases (ESR): Firefox 78 is the first ESR release that supports Service workers (and the Push API). Earlier ESR releases had no support (bug 1547023).

WebAssembly

  • 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 (bug 1628321).
  • WebAssembly now supports import and export of 64-bit integer function parameters (i64) using BigInt from JavaScript (bug 1608770).

TLS 1.0 and 1.1 removal

Firefox developer tools

Download Mozilla Firefox Developer

  • Support for the Transport Layer Security (TLS) protocol’s version 1.0 and 1.1, is dropped from all browsers. Read TLS 1.0 and 1.1 Removal Update for the previous announcement and what actions to take if you are affected (bug 1643229).

Changes for add-on developers

  • browsingData.removeCache and browsingData.removePluginData now support deleting by hostname. (bug 1636784).
  • When using proxy.onRequest, a filter that limits based on tab id or window id is now correctly applied. This could be useful for add-ons that want to provide proxy functionality just in just one window.
  • Clicking within the context menu from the 'all tabs' dropdown now passed the appropriate tab object. In the past, the active tab was erroneously passed.
  • When using downloads.download with the saveAs option, the recently used directory is now remembered. While this information is not available to developers, it is very convenient to users.

Download Mozilla Firefox Developer Version

See also

Older versions