Good purpose

very good

Randomly changes active page with "Page not available?" message even tho page is still available, just loading

Ok. This extension used to be *bad*. It was limited in its use and had a serious problem with what I'm terming "archive misfire", where it would decide to redirect some pages (which would otherwise load just fine!) to a new page where it gave you the option to view it in the archive. When you didn't need to.
Yet now! As of February this year, the extension has leapt all the way from version 1.8.6 to version 3.0, and let me tell you, this version absolutely slaps. It's brilliant. Archive misfire is no more, and it's got all sorts of helpful little options. The Internet Archive has taken this extension from an over-agressive bookmarklet to a really quite helpful browsing tool. If you scorned this extension before, I invite you to give it another go; and if you're here for the first time, don't be scared off by the review score - truly, things are better now. Also, some other reviews mention needing to login to save pages, a requirement which has been lifted as of ~a month ago.

Generally works well. It falls short in:
- Frequently auto-updating and then not operating at all until the user agrees to new permissions, which is a drag on workflow.
- Persists in annoying me with pop-up boxes to "check out more great features in settings," which is obnoxious when commercial software does it, let alone when a utility put out by a non-profit does. It should do its job and get out of my way.

This is a great extension. It is much quicker to save a page than it used to be, and has quick links to archived versions of pages. The auto-archive feature is brilliant.

С нового обновления требует залогиниться.

You need to login to save a page & the last 3 or 4 updates are really bad for privacy.
I used it since it was a test-pilot program for Firefox in 2016 (no more 404s). But since all new "features" are really bad I uninstalled it.

You need to log in order to save anything.

The add-on now forces you to log in to archive a page, but previous versions (and the archive.org website) have no such requirement. This login requirement is a serious regression that prevents me from using this version at all. I'm not going to create an account for no reason; I'd prefer to remain anonymous. I've reverted back to version 1.8.6 (which is still available here under "See all versions").

Everytime I go to my Banks website this plugin rediects me to its own page. Removed plugin from Firefox

Version 3.0 works fine here!
With the new feature, which shows saved status of the page right away, now it is very easy to make a decision whether or not to save the page. To do this with prior versions, I had to first check the newest saved page and to see if it exists or not. The saving process is being done in background, so I can browse other pages while the add-on saves a page.

(Below is my review a year ago about previous version)
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Once worked fine, but for the past few months, it has got "Fail with status: 498 No Reason Phrase" error with Retry button, which fails all the time on firefox (waterfox as well). So, now this extension is quite useless and needs to be updated.