Chrome 88 Highlights: Manifest v3, CSS aspect‑ratio, Timer Throttling & Removed Features

On January 19, 2021, Chrome released version 88, completing several major deprecation plans including FTP, Flash, WebComponents v0, and mixed‑content downloads.

New Stable Features

Manifest v3

Chrome 88 now supports extensions built with Manifest v3, which can be uploaded to the Chrome Web Store. Manifest v3 offers a more secure, efficient, and privacy‑respectful extension platform. It disallows remotely hosted code, helping reviewers assess risks and enabling faster updates. It also introduces service workers to replace background pages, reducing memory usage.

For migration details, see the official documentation.

CSS aspect‑ratio Property

Previously, only certain elements like <img> had an intrinsic aspect ratio. Chrome 88 adds the aspect-ratio property, allowing explicit width‑to‑height ratios.

<!-- Height is auto‑computed from width & aspect ratio -->
<img src="..." style="width: 800px;">

Example CSS:

.square {
  aspect-ratio: 1 / 1;
}

For progressive enhancement, you can use the CSS4 :not selector:

.square {
  aspect-ratio: 1 / 1;
}
@supports not (aspect-ratio: 1 / 1) {
  .square {
    height: 4rem;
    width: 4rem;
  }
}

Demo available via the provided link.

Significant Limitation of Chained JavaScript Timers

To reduce CPU and battery usage, Chrome has been optimizing hidden pages since version 87. In version 88, chained JavaScript timers are heavily throttled under certain conditions.

let chainCount = 0;
function setTimeoutChain() {
  setTimeout(() => {
    chainCount++;
    console.log(`This is number ${chainCount} in the chain`);
    setTimeoutChain();
  }, 500);
}

The throttling applies when all of the following are true:

The page has been hidden for more than 5 minutes.

The chain count is 5 or more.

The page has been muted for over 30 seconds.

WebRTC is not used.

In this scenario, Chrome checks timers once per minute and batches their execution. The official recommendation is to use setInterval instead.

More information is available in the Chrome blog post.

Deprecated & Removed Features

Pop‑ups Disallowed on Page Unload

Since Chrome 80, window.open cannot be used during page unload. Enterprise users could enable it via the AllowPopupsDuringPageUnload flag, which is also removed in Chrome 88.

Fully Disabled FTP

Due to low usage, bugs, and security concerns, FTP support has been phased out. Chrome 86 introduced experimental disabling, Chrome 87 disabled it for 50% of users (with a flag to re‑enable), and Chrome 88 removed FTP entirely.

Fully Disabled Flash

Chrome 83 added stricter prompts for Flash activation. Flash reached end‑of‑life on December 31, 2020, and Adobe stopped supporting it on January 12, 2021.

Fully Disabled Mixed‑Content Downloads

Starting with Chrome 81, mixed‑content downloads were progressively blocked, culminating in a complete block for all file types in Chrome 88.

Removal of WebComponents v0

WebComponents v0 was deprecated starting with Chrome 80 and fully removed in Chrome 88, with WebComponents v1 taking its place and supported across Safari, Firefox, and Edge.