Key takeaways: The Search Terms field takes 250 bytes, not 250 characters, and going over can stop the whole field indexing. Fill it with words that appear nowhere else in the listing: synonyms, regional spellings, related use cases. Leave out brand names, ASINs, repeats of the title, punctuation and anything subjective. Verify indexing 48 hours later.
What the field is and where it lives
In Seller Central, open the listing, go to the Product Details or Keywords tab, and you will find the field labeled Search Terms (in some templates, Generic Keywords). Shoppers never see it. Amazon's search engine reads it and treats the words as additional terms your ASIN can match. It is the one place in a listing where you write for the algorithm alone, so it should not repeat what the buyer already reads elsewhere.
Bytes, not characters
Amazon's limit for the field is fewer than 250 bytes. For plain English letters and digits, one character is one byte, so the limit feels like 250 characters. Accented letters, umlauts and most non-Latin scripts use two or more bytes per character. A German or Arabic listing runs out of room faster than the character count suggests.
Amazon's own guidance says that if the field exceeds the limit, the terms may not be indexed at all. This is the most common backend mistake we find in audits: a 300-character field that a seller believes is working and that has been silently ignored for a year. Count bytes with a simple tool, or keep English fields under 240 characters to leave margin.
What goes in
The rule is simple: only words that do not already appear in the title, bullets, description or structured attributes. Amazon indexes those fields already, so repeating them here wastes bytes.
Good candidates:
- Synonyms and alternative names. "Flask" and "thermos" for a bottle listing that says "bottle" everywhere else.
- Regional and alternate spellings. "Colour", "grey", "aluminium" for a US listing that uses American spelling in the copy.
- Use cases and audiences the copy did not cover. "Camping", "dorm", "nurses".
- Compatible items described generically. "Fits standard cup holder" if that phrase is not in a bullet.
- Category-adjacent terms buyers use loosely. A "desk organizer" that shoppers also search as "pen holder".
Separate words with single spaces. Amazon matches individual words and combinations, so "insulated steel flask" covers "steel flask" and "insulated flask" as well. Do not repeat a word to strengthen it; once is indexed, twice is wasted.
What stays out
| Leave out | Reason |
|---|---|
| Your own brand name | Already indexed from the brand field |
| Competitor brand names | Prohibited by Amazon; can trigger listing action |
| ASINs, UPCs, model numbers already in the listing | Duplicates; ASINs are prohibited |
| Punctuation, commas, semicolons | Not needed; spaces are enough, and punctuation burns bytes |
| Both singular and plural of the same word | Amazon matches the other form automatically |
| Subjective or temporary words: "best", "cheap", "new", "sale" | Prohibited as subjective or temporary claims |
| Common misspellings | Amazon's guidance says they are not needed |
| Profanity or offensive terms | Prohibited |
| Stop words: "a", "the", "for", "with" | Ignored by search, so they only use bytes |
Amazon has stated it does not index prohibited terms even when they fit, and repeated violations can affect listing health. Stuffing competitor brands into the field is the black-hat tactic that most often leads to a policy notice.
The process we follow
Read this flowchart as text
- Tiered keyword list from research
- Remove every word already in title, bullets, description, attributes
- Remove brands, ASINs, subjective, temporary and stop words
- Order by search volume, one form of each word
- Under 250 bytes with margin?
- Drop lowest-volume words from the end
- Upload and log the version
- Check indexing after 48 hours in Search Query Performance
We keep a dated copy of every backend field we upload. Amazon can revert or overwrite attribute data during catalog updates, and a version log is the only way to notice when a field that used to index has emptied.
Other hidden fields that index
The Search Terms field is not the only invisible input. Structured attributes such as material, color, size, target audience, item form and style are indexed and also power the filters in the left rail. A listing with "stainless steel" only in the backend field misses the material filter; a listing with the attribute set matches both. Fill the structured fields first, then use the backend field for what has no field of its own. With Amazon's move toward semantic matching, described in Amazon COSMO Explained: How Semantic Search Changes Ranking, structured attributes matter more each year, not less.
Subject Matter and Platinum Keywords fields exist in some templates. Platinum Keywords are for Platinum merchants only and do nothing for most sellers; leave them blank.
The keyword and indexing process the backend field belongs to is here.
Frequently asked questions
Does the order of words in the backend field matter?
Not for indexing. Amazon matches words in any order and in any combination. We order by search volume only so that if we have to trim to fit the byte limit, the least valuable words go first.
Should I put keywords in Spanish or other languages in a US listing?
Only if Search Query Performance shows real searches in that language for your product. Amazon does translate queries in some marketplaces, but where a specific non-English term has volume, one word of it in the backend field is a legitimate use of bytes.
How often should I update backend search terms?
Review them when you review the keyword list, typically monthly, and whenever a new term shows volume in Search Query Performance that the listing does not index for. Changing the field weekly gives Amazon nothing extra and makes it hard to attribute indexing changes.
Can I see which backend terms are working?
Not directly. Search Query Performance shows the queries your ASIN appeared for; if a query contains a word that exists only in your backend field, the field is doing its job. The check method is in How to Check If Your Amazon Listing Is Indexed for a Keyword.