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Merged
pepelsbey merged 3 commits into from
May 5, 2026
+2 −63
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Firefox experimental features clean-up #43887

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36dd01d
updated the entries in firefox experimental features
dletorey Apr 21, 2026
7252b1a
Merge branch 'main' into ff-exp-features
dletorey Apr 21, 2026
1725079
Merge branch 'main' into ff-exp-features
dletorey May 1, 2026
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65 changes: 2 additions & 63 deletions files/en-us/mozilla/firefox/experimental_features/index.md
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Original file line number Diff line number Diff line change
Expand Up @@ -183,7 +183,7 @@ See ([Firefox bug 1737920](https://bugzil.la/1737920)) for more details.

| Release channel | Version added | Enabled by default? |
| ----------------- | ------------- | ------------------- |
| Nightly | 114 | No |
| Nightly | 136 | Yes |
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| Developer Edition | 114 | No |
| Beta | 114 | No |
| Release | 114 | No |
Expand All @@ -199,7 +199,7 @@ See ([Firefox bug 1808410](https://bugzil.la/1808410)) for more details.

| Release channel | Version added | Enabled by default? |
| ----------------- | ------------- | ------------------- |
| Nightly | 114 | No |
| Nightly | 136 | Yes |
| Developer Edition | 114 | No |
| Beta | 114 | No |
| Release | 114 | No |
Expand Down Expand Up @@ -230,21 +230,6 @@ Specifically, this preference will disable the following prefixed properties:
- `layout.css.prefixes.transforms`
- : Set to `true` to enable.

#### Relative control points in CSS `shape()` curve commands

You can use [`<relative-control-point>`](/en-US/docs/Web/CSS/Reference/Values/basic-shape/shape#relative-control-point) values when specifying a [`<curve-command>`](/en-US/docs/Web/CSS/Reference/Values/basic-shape/shape#curve-command) or [`<smooth-command>`](/en-US/docs/Web/CSS/Reference/Values/basic-shape/shape#smooth-command) in a CSS `shape()` function. These values let you specify control points that are positioned relative to the start or end point of the current command, or relative to the origin (top-left) of the container the shape is being drawn inside.
([Firefox bug 1921501](https://bugzil.la/1921501)).

| Release channel | Version added | Enabled by default? |
| ----------------- | ------------- | ------------------- |
| Nightly | 146 | Yes |
| Developer Edition | 146 | No |
| Beta | 146 | No |
| Release | 146 | No |

- `layout.css.basic-shape-shape.enabled`
- : Set to `true` to enable.

### Symmetrical `letter-spacing`

The CSS {{cssxref("letter-spacing")}} property now splits the specified letter spacing evenly on both sides of each character. This is unlike the current behavior where spacing is added primarily to one side. This approach can improve text spacing, especially in mixed-directional text.
Expand All @@ -260,20 +245,6 @@ The CSS {{cssxref("letter-spacing")}} property now splits the specified letter s
- `layout.css.letter-spacing.model`
- : Set to `true` to enable.

### `calc()` color channel support in relative colors

The CSS {{cssxref("calc()")}} function can now parse color channels in [relative colors](/en-US/docs/Web/CSS/Guides/Colors/Using_relative_colors#using_math_functions), allowing you to correctly calculate changes to colors in different color spaces or while using different functional notations [Firefox bug 1889561](https://bugzil.la/1889561).

| Release channel | Version added | Enabled by default? |
| ----------------- | ------------- | ------------------- |
| Nightly | 127 | Yes |
| Developer Edition | 127 | No |
| Beta | 127 | No |
| Release | 127 | No |

- `layout.css.relative-color-syntax.enabled`
- : Set to `true` to enable.

### Allow pseudo-elements after element-backed pseudo-elements

Work has started on allowing [pseudo-elements](/en-US/docs/Web/CSS/Reference/Selectors/Pseudo-elements) such as {{cssxref("::first-letter")}} and {{cssxref("::before")}} to be appended to [element-backed pseudo-elements](/en-US/docs/Web/CSS/Reference/Selectors/Pseudo-elements#element-backed_pseudo-elements) such as {{cssxref("::details-content")}} and {{cssxref("::file-selector-button")}}.
Expand Down Expand Up @@ -305,20 +276,6 @@ The {{cssxref(":heading")}} pseudo-class allows you to style all [heading elemen
- `layout.css.heading-selector.enabled`
- : Set to `true` to enable.

### `text-decoration-trim`

The CSS `text-decoration-trim` property allows you to specify {{cssxref("text-decoration")}} start and end offsets to shorten, lengthen, or shift the position of text decorations with respect to the text ([Firefox bug 1979915](https://bugzil.la/1979915)).

| Release channel | Version added | Enabled by default? |
| ----------------- | ------------- | ------------------- |
| Nightly | 145 | No |
| Developer Edition | 145 | No |
| Beta | 145 | No |
| Release | 145 | No |

- `layout.css.text-decoration-trim.enabled`
- : Set to `true` to enable.

### `@custom-media` at-rule

The {{cssxref("@custom-media")}} CSS at-rule defines aliases for long or complex media queries. Instead of repeating the same hardcoded `<media-query-list>` in multiple `@media` at-rules, it can be defined once in a `@custom-media` at-rule and referenced throughout the stylesheet whenever needed. ([Firefox bug 1744292](https://bugzil.la/1744292)).
Expand Down Expand Up @@ -749,24 +706,6 @@ When `Integrity-Policy` is used, the browser blocks the loading of styles refere
- `security.integrity_policy.stylesheet.enabled`
- : Set to `true` to enable.

### Storage Access headers

The {{httpheader("Sec-Fetch-Storage-Access")}} and {{httpheader("Activate-Storage-Access")}} HTTP headers are now supported, enabling a more efficient [Storage Access API](/en-US/docs/Web/API/Storage_Access_API) workflow. ([Firefox bug 1991688](https://bugzil.la/1991688)).

In the JavaScript-only workflow, a third-party resource must be requested and loaded to activate a storage-access permission for a particular context (such as a new browser tab). This is required even if the permission has already been granted.
The storage access headers allow the browser to advertise the permission state for the particular context, so the server can request activation of an already-granted permission.
This avoids the overhead of unnecessarily fetching and loading the resource.

| Release channel | Version added | Enabled by default? |
| ----------------- | ------------- | ------------------- |
| Nightly | 145 | Yes |
| Developer Edition | 145 | No |
| Beta | 145 | No |
| Release | 145 | No |

- `dom.storage_access.headers.enabled`
- : Set to `true` to enable.

### Idempotency-Key

The {{httpheader("Idempotency-Key")}} HTTP request header can be used by website client code to make a {{HTTPMethod("POST")}} or {{HTTPMethod("PATCH")}} requests {{glossary("idempotent")}} when used with a server that supports it.
Expand Down
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