An Etsy research extension does one thing: it puts data on top of the page you are already looking at, so you stop copying URLs into a second tool. That is a small idea with a large effect on how fast you can work, and there are now enough of them that choosing badly is easy.
What an Etsy extension can and cannot know
This matters more than any feature list, so it goes first.
It can read anything on the public page: title, tags, price, review count, favorites, shop age, listing age, photos. All of that is real, verifiable data, and any tool showing it is showing you a fact.
It cannot see real sales. Etsy does not publish per-listing sales figures, to anyone, through any channel. Every "estimated sales" number in every extension is inferred from the public signals above. That does not make estimates useless, it makes the method and the uncertainty the things worth comparing.
What to look for
Stated confidence
A listing with three years of history and 400 reviews supports a very different estimate than one published last month with four. If both produce the same confident number, the tool is hiding its uncertainty from you rather than not having any.
Permissions that make sense
An Etsy extension needs access to etsy.com pages and local storage. It does not need your browsing history, your bookmarks, or access to every site you visit. Chrome shows the permission list at install time. Read it.
It should never ask for your Etsy password
Connecting your own shop should go through Etsy's official OAuth, read-only. Any tool that asks you to type your Etsy credentials into its own form should be uninstalled immediately, whatever it promises.
Speed and sleep
A good extension runs on listing, shop and search pages and stays out of the way everywhere else, especially your own shop dashboard. If it makes Etsy visibly slower, it will cost you more time than it saves.
Data you can act on
Tags and title structure of ranking listings tell you what to write. Favorites over time tell you whether interest is growing. A single revenue estimate, on its own, mostly tells you whether to feel good or bad.
The main options
EverBee is the best known, with a very large user base and a fast in-page panel focused on estimated sales and revenue. Strong at what it does; presents estimates with more confidence than the underlying evidence always supports.
Sale Samurai covers keyword and tag research in-page, with a broad feature set and a busier interface.
eRank is primarily a web app rather than an extension, and remains the reference for keyword volume research at low cost.
ZeusLens is the extension half of ZEUS AI. Its distinguishing choice is calibrated confidence on every estimate, plus a shared database with the full platform so the market history behind a listing is the same data the platform reasons over. It is also the newest of the four, with the smallest track record, which is a real disadvantage worth stating.
A fuller side-by-side of the three platforms is in EverBee vs eRank vs ZEUS.
Testing one before you trust it
Install it, then point it at listings whose real numbers you already know: your own. If the estimates on your own products are wrong, they are wrong on everyone else's too, and you have learned that in five minutes at no cost.
Then check three things over a week of normal use. Does it slow Etsy down. Does it disagree with itself between the listing page and the search page. Does it ever say "not enough data", or does it always produce a number no matter how thin the evidence.
That third test is the one that separates a research tool from a confidence generator.