Amazon backend keyword checker (249-byte validator)
Paste your generic keywords and get the exact UTF-8 byte count plus the full 8-rule compliance check — instantly, in your browser.
Why your backend search terms probably fail silently
The backend generic-keywords field is the only part of your listing shoppers never see — and the only one measured in UTF-8 bytes, not characters. Exceed the budget and Amazon can ignore the field entirely, with no error, no warning, and no way to tell from Seller Central. Sellers routinely paste 300+ bytes of keywords, see the save succeed, and index for none of them.
The second silent failure is duplication: words that already appear in your title, bullets or description gain nothing by being repeated in the backend. Every duplicated word is a wasted byte that could have been a synonym, a misspelling your customers actually type, or a use-case term your visible copy can’t fit.
The 8 rules this checker runs
This is the exact validator our AI pipeline runs on every backend field it generates — published here as a free tool. It checks: the 249-byte UTF-8 budget, no repeated words, no punctuation, no articles/prepositions/conjunctions, all lowercase, no ASINs, no subjective or temporary claims (best, new, premium, sale…), and the inclusion rule — no overlap with your visible copy. Paste your terms, fix what’s red, and use the one-click cleanup as a starting point.
Frequently asked questions
Why does Amazon count bytes instead of characters?
The generic-keywords (backend search terms) field is limited by its UTF-8 encoded size. Plain English letters are 1 byte each, but accented characters like é, ü or ñ take 2+ bytes — so a German or Spanish keyword list can blow the limit while a character counter still shows you as safe. This checker counts real UTF-8 bytes, exactly like the limit works.
Do spaces count toward the 249-byte limit?
Amazon's public guidance on this has varied over the years, so this checker counts every byte including spaces — the strictest reading. If your keywords pass here, they fit under any interpretation, which is the only safe way to validate a field you can't debug from the outside.
Should backend keywords repeat words from my title or bullets?
No. Amazon indexes your visible copy already, so repeating those words in the backend adds zero new indexing and wastes your very limited byte budget. That's the inclusion rule this checker enforces: backend keywords should only contain terms ABSENT from your title, bullets and description — synonyms, alternate spellings, regional terms and use-case words.
Do I need commas between backend keywords?
No — separate keywords with single spaces only. Commas, semicolons and other punctuation are unnecessary, and this checker flags them so every byte goes to an actual keyword.
Is my listing data uploaded anywhere?
No. The checker runs entirely in your browser — your keywords and listing copy never leave the page. There's no signup and nothing is stored.
More free Amazon tools
Backend keywords are one field. A listing is eleven.
Listing Revamp analyzes your competitors' reviews and keywords, then writes the whole listing — title, bullets, description AND a compliant backend field that passes all 8 of these rules on the first try.
No credit card, no API key — the free plan includes AI.