Why did Imagus stop working?

Usually one of three things. Its sieve rules are out of date for a site that redesigned, which shows up as failures on some sites but not others. The browser disabled or restricted the extension, which shows up as total failure everywhere. Or the site now serves images in a way the installed rule set does not recognise. Checking whether previews still work on a second, unrelated site tells you which category you are in within seconds.

How do I update Imagus sieve rules?

Open the Imagus options page and look for the sieve or rules section, which offers an update or import action. Community-maintained rule sets are shared on the Imagus forums and GitHub. If an updated rule set does not fix the site, the rule for that site has not been written yet by anyone.

Can I move my Imagus sieve rules to another extension?

Ultra Zoom supports custom URL rules in the same spirit as Imagus sieves: a pattern that matches a thumbnail URL and a replacement that produces the full-resolution URL. Most single-line sieve rules translate directly. Rules that rely on Imagus-specific scripting need rewriting, though in many cases a built-in Ultra Zoom plugin already covers that site.

Is Imagus safe to keep using?

Imagus itself was not part of the Hover Zoom data-selling scandal. The thing worth checking is maintenance: look at the last-updated date on the store listing, because a hover-zoom extension that is not updated accumulates broken sites permanently and cannot be patched if a security issue is found.

Troubleshooting

Imagus not working

Imagus previews stop appearing for three reasons, and they need completely different responses. The fastest way to tell them apart takes about thirty seconds. Work through this in order rather than reinstalling first — a reinstall wipes your sieve rules and fixes none of the three.

Step 1: does it fail everywhere, or only on some sites?

Open two unrelated image-heavy sites — a Google Images results page and a Reddit thread are a good pair. Hover a thumbnail on each.

One works, one does not — Imagus is running correctly and its rule for the broken site is out of date. Go to step 3.
Neither works — the extension itself is not running. Go to step 2.

This one test rules out most of the wrong answers, which matters because “Imagus is broken” and “Imagus has not learned about a site’s redesign yet” look identical from the outside.

Step 2: confirm the extension is actually running

Check it is enabled. Open your extensions page — chrome://extensions or about:addons. A browser update can disable an extension that no longer meets store policy, and it does so without a notification you are likely to see.
Check its site permissions. Chromium browsers let you restrict an extension to specific sites, and a setting of On click means it does nothing until you click the toolbar icon. Set it to run on the site you are testing.
Check for Manifest V2. If the extensions page flags it as an older-format extension, you are hitting the Manifest V3 transition and there is nothing to configure — see what Manifest V3 broke for why hover-zoom tools were hit especially hard.
Test in a clean profile. Another extension — particularly an aggressive content blocker or a userscript manager — can suppress the overlay. A fresh browser profile with only Imagus installed settles that question quickly.

Step 3: update the sieve rules

Imagus keeps its site knowledge in sieve rules: a pattern that matches a thumbnail URL and a replacement that produces the full-resolution URL. When a site changes its image CDN or markup, the rule stops matching and previews go quiet on that site alone.

Open the Imagus options page and look for the sieve or rules section, which offers an update or import action. Community-maintained rule sets circulate on the Imagus forums and on GitHub. Reload the page you were testing afterwards — rules are applied at page load.

If an up-to-date rule set still does not fix the site, no one has written a working rule for it yet. That is the point at which the maintenance question stops being academic.

Step 4: check whether anyone is still maintaining it

Look at the last-updated date on the Chrome Web Store or Firefox Add-ons listing. This is the single most useful number in this whole process, because both of the fixable causes above depend on someone shipping updates.

An unmaintained hover-zoom extension does not fail all at once. It degrades: one site breaks, then another, and each broken site is permanent. If the listing shows no release in two or more years, the rules you need are not coming.

Migrating your sieve rules

Ultra Zoom supports custom URL rules built on the same idea as Imagus sieves — a match pattern and a replacement that yields the full-resolution URL — so most single-line sieves translate more or less directly. Rules that lean on Imagus-specific scripting need rewriting, but in a lot of cases you will not need to: if a site was common enough for someone to write a sieve for it, there is a decent chance Ultra Zoom already ships a maintained plugin for it. Check the supported sites list before you port anything.

What actually transfers is the workflow, which is the part you have muscle memory for: hover to preview, arrow keys through a gallery, scroll to zoom, and a theater mode for a closer look. The full feature-by-feature comparison covers where the two differ, and the alternatives roundup covers the options that are not us.

Try Ultra Zoom free

Free forever on the majority of supported sites, with no account required to install. If a site you rely on is not covered, send us the URL — that is how most plugins get written.