| # Permissions-Policy: Unload |
| |
| Contact: bfcache-dev@chromium.org |
| |
| This document describes the status of the current implementation of the |
| [Permissions-Policy: unload feature](https://github.com/w3c/webappsec-permissions-policy/issues/444) |
| in Chrome, and how to enable it. |
| |
| Starting from version 107, |
| Chrome experimentally supports Permissions-Policy: unload. |
| This allows sites to prevent usage of unload event listeners. |
| |
| Note that this policy is not available by default. |
| Chrome plans to do an origin trial |
| to evaluate its effectiveness |
| and to allow site authors to give feedback. |
| |
| ## What’s supported |
| |
| A new [permission](https://github.com/w3c/webappsec-permissions-policy/blob/main/permissions-policy-explainer.md) is added, `unload`, |
| which defaults to be enabled |
| but when disabled makes calls to `window.addEventListener("unload", callback)` |
| a no-op. |
| |
| ## What’s not supported |
| |
| |
| ## Activation |
| |
| The policy can be enabled in several ways. |
| |
| ### Using command line flag |
| |
| Pass the `--enable-features=PermissionsPolicyUnload` command line flag. |
| |
| ### Using the Chromium UI |
| |
| Enable the flag chrome://flags/#enable-experimental-web-platform-features . |
| |
| ### Using Origin Trial |
| |
| The [Origin Trial](https://developer.chrome.com/blog/origin-trials/) feature is named `PermissionsPolicyUnload`. |
| Registration for the trial is [here](https://developer.chrome.com/origintrials/#/view_trial/1012184016251518977). |
| See [feature status](https://chromestatus.com/feature/5760325231050752) to find out |
| if the origin trial is currently running. |
| |
| The [origin trial tutorial](https://developer.chrome.com/docs/web-platform/origin-trials/#take-part-in-an-origin-trial) describes how to participate. |
| |
| ### Verifying the API is working |
| |
| In devtools, run the following piece of javascript |
| |
| ```js |
| document.createElement("iframe").allow="unload"; |
| ``` |
| |
| If it succeeds then the feature is enabled. |
| If it gives an error like |
| `Unrecognized feature: 'unload'.` |
| then the feature is not enabled. |
| |
| ## Related Links |
| |
| - [Chrome Status](https://chromestatus.com/feature/5760325231050752) |
| - [Permissions-Policy: unload Explainer](https://github.com/fergald/docs/blob/master/explainers/permissions-policy-unload.md) |
| - [Permissions-Policy: Explainer](https://github.com/w3c/webappsec-permissions-policy/blob/main/permissions-policy-explainer.md) |
