Firefox 80 for developers
=========================

This article provides information about the changes in Firefox 80 that will affect developers. Firefox 80 was released on August 25, 2020.

Changes for web developers
--------------------------

### Developer Tools

* You can now block and unblock network requests using the `:block` and `:unblock` helper commands in the Web Console (Firefox bug 1546394).
* When adding a class to an element in the Page Inspector's Rules pane, existing classes are suggested with autocomplete (Refer to Firefox bug 1492797).
* When the Debugger breaks on an exception, the tooltip in the source pane now shows a disclosure triangle that reveals a stack trace (Firefox bug 1643633).
* In the Network Monitor request list, a turtle icon is shown for "slow" requests that exceed a configurable threshold for the waiting time (Firefox bug 1648373).
### HTML

*No changes.*

### CSS

* The standard, unprefixed `appearance` property is now supported; existing `-moz-appearance` and `-webkit-appearance` are now aliases of the unprefixed property (Firefox bug 1620467).
### JavaScript

* The ECMAScript 2021 `export * as namespace` syntax for the `export` statement is now supported (Firefox bug 1496852).
### HTTP

* Previously, when the fullscreen directive was applied to an `<iframe>` (i.e. via the `allow` attribute), it didn't work unless the `allowfullscreen` attribute was also present This has now been fixed (Firefox bug 1608358).
### APIs

#### DOM

* Web Animations API compositing operations are now enabled — see `KeyframeEffect.composite` and `KeyframeEffect.iterationComposite` (Firefox bug 1652676).

#### Removals

* The `outerHeight` and `outerWidth` features of `Window.open()` are no longer exposed to web content (Firefox bug 1623826).
### WebAssembly

* Atomic operations are now allowed on non-shared memories (Firefox bug 1619196).
### WebDriver conformance (Marionette)

* Using `WebDriver:NewWindow` to open a new tab no longer returns too early when running tests in headless mode (Firefox bug 1653281).
* We removed the `name` argument for `WebDriver:SwitchToWindow` — it is not supported for W3C-compatible mode, and shouldn't be used anymore (Firefox bug 1588424).
* We've started to add Fission support for the following commands: `WebDriver:FindElement`, `WebDriver:FindElements`, `WebDriver:GetElementAttribute`, `WebDriver:GetElementProperty`.
* **Known issue**: Opening a new tab by using `WebDriver:NewWindow`, or via an arbitrary script that calls `window.open()`, now automatically switches to that new window (Firefox bug 1661495).
Changes for add-on developers
-----------------------------

*No changes.*

Older versions
--------------

* Firefox 79 for developers
* Firefox 78 for developers
* Firefox 77 for developers
* Firefox 76 for developers
* Firefox 75 for developers
* Firefox 74 for developers
* Firefox 73 for developers
* Firefox 72 for developers
* Firefox 71 for developers
* Firefox 70 for developers
* Firefox 69 for developers
* Firefox 68 for developers
* Firefox 67 for developers
* Firefox 66 for developers
* Firefox 65 for developers
* Firefox 64 for developers
* Firefox 63 for developers
* Firefox 62 for developers
* Firefox 61 for developers
* Firefox 60 for developers
* Firefox 59 for developers
* Firefox 58 for developers
* Firefox 57 for developers
* Firefox 56 for developers
* Firefox 55 for developers
* Firefox 54 for developers
* Firefox 53 for developers
* Firefox 52 for developers
* Firefox 51 for developers
* Firefox 50 for developers
* Firefox 49 for developers