Amazon Search Terms Byte Counter
Amazon limits backend search terms by bytes, not characters — and one byte over can stop the entire field from being indexed. Paste your keywords to see the real budget, which words cost the most, and 13 rules worth of waste.
🔒 Your data never leaves your browser.
Every check this tool runs (13 rules)
Rules come from Amazon's own guidance on search terms. Each one lists what it checks, why it matters and how to fix it — nothing here is guesswork about the ranking algorithm. Amazon's help centre sits behind a seller login, so we name the source document rather than link you to a page that would just show you the Seller Central homepage.
Byte budget
STB-001 Over the 249-byte limit
Backend search terms are limited by BYTES, not characters. Going over means Amazon may ignore the ENTIRE field — not just the overflow — so every keyword stops working. The limit is under 250 bytes (i.e. 249 max) on most marketplaces.
Fix: Remove the lowest-value keywords until you are within budget. Watch accented and non-Latin characters: each one costs 2–4 bytes.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STB-002 Close to the byte limit
You are within 10% of the byte limit. Adding one accented or non-Latin word can silently push you over, which disables the whole field.
Fix: Leave headroom, or verify the byte count again after every edit.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
Content rules
STC-001 Duplicate words waste bytes
Repeating a word in the search terms field adds nothing to indexing — Amazon already indexes each word once. Every repeat is bytes spent for zero reach.
Fix: Delete the repeats and spend the bytes on keywords you have not covered yet.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STC-002 Commas and punctuation waste bytes
Amazon asks for keywords separated by single spaces. Commas, semicolons and pipes are not needed as separators and consume bytes that could hold real keywords.
Fix: Separate keywords with a single space.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STC-003 Word already in the product title
Words in your title are already indexed. Repeating them in backend search terms spends bytes without adding any new search coverage.
Fix: Drop title words from the backend field and use the space for synonyms, misspellings and use-cases.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STC-004 Singular and plural of the same word
Amazon matches singular and plural forms, so including both is redundant for most words.
Fix: Keep one form and reclaim the bytes.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STC-005 Contains an ASIN
ASINs (and other product identifiers) are not allowed in backend search terms and can trigger listing suppression.
Fix: Remove the ASIN.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STC-006 Subjective or promotional claim
Temporary or subjective terms ("best", "cheapest", "new", "sale", "#1") are not allowed in search terms and do not help ranking.
Fix: Replace with concrete attributes buyers actually type: material, size, use-case, compatibility.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STC-007 Looks like a competitor brand or trademarked term
Brand names you do not own are not permitted in search terms and are a frequent cause of listing takedowns. This rule only fires for terms you explicitly list as brands to avoid — this tool cannot know every trademark, so an empty result is not a clearance.
Fix: Remove the branded term. Describe the product instead: "case for 6.1 inch phone" rather than a brand name.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STC-008 Very long single token
A single "word" longer than 30 characters is usually a concatenated phrase, a URL, or a pasting accident. Buyers never type it, and it can consume a large share of your byte budget.
Fix: Split it into the words buyers actually search for, or delete it.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
Characters & language
STL-001 Non-ASCII characters cost extra bytes
Accented Latin (é, ñ), Cyrillic and CJK characters take 2–4 bytes each in UTF-8, so a "short" keyword can be surprisingly expensive. This is why character counters mislead sellers.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STL-002 Full-width characters detected
Full-width digits and letters (１２３, ＡＢＣ) cost 3 bytes each and are not what buyers type. They usually arrive by accident from CJK input methods.
Fix: Convert them to normal half-width characters.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
STL-003 Invisible or zero-width characters
Zero-width spaces, non-breaking spaces and BOM markers are invisible but still consume bytes — and can split a keyword so it never matches.
Fix: Retype the affected keywords or clean the text before pasting.
Source: Amazon Seller Central Help → "Use search terms effectively" (the Seller Central help centre requires a seller login, so we describe the source instead of linking to a page that would show you the homepage).
Why bytes, not characters?
A character counter tells you how many letters you typed. Amazon measures how much space those letters occupy in UTF-8, and not every character costs the same:
| Characters | Bytes each | Example |
|---|---|---|
| Plain English letters, digits, spaces | 1 | bottle = 6 bytes |
| Accented Latin, Greek, Cyrillic | 2 | niños = 5 characters but 6 bytes |
| CJK, most symbols, full-width forms | 3 | ボトル = 3 characters, 9 bytes |
| Emoji and rare scripts | 4 | 🍾 = 1 character, 4 bytes |
This is why sellers targeting Spanish, German, French or Japanese buyers silently blow the
budget: the field looks short, and Excel's LEN() agrees with them.
What happens if you go over
It is not a soft trim. When the field exceeds the limit, Amazon may ignore all of your backend keywords — the ones inside the budget included. That is why this tool treats overflow as an error, not a warning.
Where the bytes get wasted
Commas between keywords, words already in your title, both singular and plural of the same word, repeated words, and invisible characters pasted from spreadsheets. None of them add search coverage, and together they routinely account for a fifth of the budget.