Deprecations and removals in Chrome 73
Remove EXPLAIN and REINDEX support in WebSQL
EXPLAIN's output is not guaranteed to be stable over SQLite versions, so developers cannot rely on it. REINDEX is only useful when collation sequence definitions change, and Chrome only uses the built-in collation sequences. Both features are now removed.
Remove isomorphic decoding of URL fragment identifier
When Chrome opens a URL with a fragment id, it decodes %xx and applies isomorphic-decode to it, then tries to find an element with the decoding result as an ID in some cases. For example, if a user opens example.com/#%F8%C0, Chrome does the following:
- It searches the page for an element with id="%F8%C0".
- If it’s not found, it searches the page for an element with id="&#xF8;&#xC0;". No other browsers do this, and it's not defined by the standard. Starting in version 73, Chrome no longer does this either.
Deprecate 'drive-by downloads' in sandboxed iframes
Chrome has deprecated downloads in sandboxed iframes that lack a user gesture ('drive-by downloads'), though this restriction could be lifted via an allow-downloads-without-user-activation keyword in the sandbox attribute list. This allows content providers to restrict malicious or abusive downloads.
Downloads can bring security vulnerabilities to a system. Even though additional security checks are done in Chrome and the operating system, we feel blocking downloads in sandboxed iframes also fits the general thought behind the sandbox. Apart from security concerns, it would be a more pleasant user experience for a click to trigger a download on the same page, compared with downloads started automatically when landing at a new page, or started non spontaneously after the click.
Removal is expected in Chrome 81.
To keep the platform healthy, we sometimes remove APIs from the Web Platform which have run their course. There can be many reasons why we would remove an API, such as:
- They are superseded by newer APIs.
- They are updated to reflect changes to specifications to bring alignment and consistency with other browsers.
- They are early experiments that never came to fruition in other browsers and thus can increase the burden of support for web developers.
Some of these changes will have an effect on a very small number of sites. To mitigate issues ahead of time, we try to give developers advanced notice so they can make the required changes to keep their sites running.
Chrome currently has a process for deprecations and removals of API's, essentially:
- Announce on the blink-dev mailing list.
- Set warnings and give time scales in the Chrome DevTools Console when usage is detected on the page.
- Wait, monitor, and then remove the feature as usage drops.
You can find a list of all deprecated features on chromestatus.com using the deprecated filter and removed features by applying the removed filter. We will also try to summarize some of the changes, reasoning, and migration paths in these posts.