Amazon backend keywords: the limit, the rules, and how to fill the field
Amazon backend keywords are the search terms you add to a listing that shoppers never see. They get your product matched to searches the visible listing does not cover, as long as you stay under the limit and follow Amazon's rules.
Key takeaways
- The backend search terms field is called Generic keyword in Seller Central, and generic_keywords in flat files.
- The limit is 249 bytes. Amazon says it should be less than 250 bytes, and a field over the limit is ignored completely.
- Spaces and punctuation do not count toward the limit.
- Do not repeat words from the title, and do not include brand names, ASINs, temporary words such as "new", or claims such as "best".
- Amazon's own guidance says to use spelling variations but to skip common misspellings.
What Amazon backend keywords are
Backend keywords, also called Amazon search terms or generic keywords, are words you enter in a listing's Generic keyword field. Amazon's search engine indexes them for lexical matching between your ASIN and a shopper's query, but they do not appear anywhere on the product page.
They exist for the words that belong in search but not in front of a shopper: synonyms, abbreviations, other ways of naming the product, and uses the visible copy has no room for. The title, bullets and description are indexed too, so the backend field is where you add what those do not already say. That matters more now that Amazon caps new product titles at 75 characters including spaces, which leaves far less room for synonyms in the title itself.
Amazon may not use every term you supply. Its help page states that relevance is decided automatically and can change over time, and that terms breaking the guidelines can be dropped.
The Amazon backend keywords limit: 249 bytes
- Bytes counted = bytes of every character, excluding spaces and punctuation
- Plain English letters and digits: 1 character = 1 byte
- Accented letters such as ä: 2 bytes or more
In Amazon's "Keyword attributes explained" table, the Search Terms attribute, generic_keywords, has a length limit of 249 bytes. The same page says search terms should be less than 250 bytes, and that if the field exceeds the limit, the attribute is completely ignored by Amazon search. Going over does not cut off the extra words; it throws away the whole field.
Amazon's FAQ on the search terms page says spaces and punctuation are not counted. It also explains why the limit is in bytes rather than characters: letters a to z, A to Z and digits 0 to 9 are one byte each, while characters such as a German umlaut take two or more. The field in Seller Central stops accepting input once the byte limit is reached.
For the attributes other than search terms, Amazon indexes text up to the limit and ignores the excess. Only the search terms field is dropped completely when it runs over.
| Attribute | Field name | Limit | Note |
|---|---|---|---|
| generic_keywords | Search Terms | 249 bytes | Free text; ignored entirely if over the limit |
| item_type_keyword | Item Type Keywords | 250 bytes | Valid values from Browse Tree Guides |
| thesaurus_subject_keywords | Subject Matter | 250 bytes | Valid values from Browse Tree Guides |
| subject_keywords | Subject Keywords | 210 bytes | Media products only |
| specific_uses_keywords | Intended Use | 150 bytes | Being phased out |
| style_keywords | Style-specific Terms | 100 bytes | Apparel; valid values from Browse Tree Guides |
What Amazon says to include, and what to leave out
Amazon recommends
- Staying within the length limit
- Synonyms
- Spelling variations
- Abbreviations
- All lowercase letters
- Separating words with spaces
- Either the singular or the plural form, not both
Amazon says to avoid
- Common misspellings
- Punctuation such as semicolons, colons and dashes
- Repeating words
- Short words such as a, an, and, by, for, of, the, with
Prohibited search terms
Amazon lists these as prohibited. Using them can get the ASIN suppressed and can affect account health:
| Prohibited | Examples from Amazon's help page |
|---|---|
| Your brand or other brand names | AppleNikeAmazon |
| ASINs | Any ASIN |
| Temporary statements | newon saleavailable nowjust launchedlimited timetoday |
| Subjective claims | bestcheapestamazingfastestpopulartrending |
| Profanity and offensive terms | Including terms that promote illegal activity or intolerance |
The misspellings point is worth checking against any advice you follow. Amazon's current help page says to use spelling variations but not common misspellings.
Worked example: rewriting a backend field
The product is an insulated stainless steel water bottle. Its title, within Amazon's 75 character limit, is: Insulated Stainless Steel Water Bottle with Straw Lid, 32 Ounce.
An illustrative product, not a real listing.
Before
water bottle insulated stainless steel best water bottle new 32oz hydro flask alternative straw lid water bottles
- 97 bytes counted, so most of the field is unused
- 10 of the 17 words already appear in the title and add nothing
- "best" and "new" are prohibited: a subjective claim and a temporary statement
- "hydro flask" is another brand's name, which is prohibited
- "water bottle" appears three times, plus the plural "water bottles"
After
thermos canteen tumbler jug hydration flask gym hiking camping travel school office kids adult leakproof sweatproof bpa free cold hot drinks dishwasher safe carabiner handle spout quart liter
- 164 bytes counted, well under 249, leaving room to add terms later
- No word repeats the title, so every byte adds something new to index
- Synonyms shoppers use for the same product: thermos, canteen, tumbler, jug
- Uses and places: gym, hiking, camping, travel, school, office
- Every word describes this product; no brands, no claims, no temporary words
Where do the new words come from? From the search term report of Sponsored Products campaigns, from Amazon's search bar suggestions, and from the words customers use in reviews and questions. A term that already converts in ads but is missing from the listing is the strongest candidate.
How to add backend keywords in Seller Central
- In Seller Central, select Manage Products.
- Select the product, and from the Fix menu, click Edit.
- Click the Product details tab.
- Enter your keywords in the Generic keyword field, separated by spaces.
- Save, then check the listing is still active and searchable after the update is processed.
Menu names in Seller Central change from time to time. These steps follow Amazon's help page as of the date at the top of this guide.
Updating search terms for many ASINs
For more than a few products, Amazon's help page describes a bulk route: download a spreadsheet of existing listings with the Category Listing report, if that option is enabled under the Inventory menu in your account, then upload changes with an inventory file template using the partial update function. If the report option is not enabled, Amazon says you can ask Selling Partner Support to turn it on.
Since December 6, 2023, Amazon requires the Generic keyword field for 23 product types, including board games, blankets, balloons, bedding sets, body care products and party favors. Listings in those product types cannot leave the field empty.
Seven common backend keyword mistakes
Going over 249 bytes
The whole field is ignored, not just the words past the limit.
Repeating the title
Words already in the title are already indexed. Repeating them spends bytes on nothing.
Competitor brand names
Prohibited, and a risk to the listing and the account.
Commas and separators
They are not needed; spaces separate the terms.
Both singular and plural
Amazon's guidance is to use one or the other.
Typos on purpose
Amazon's help page says not to include common misspellings.
Setting it once and never revisiting
New converting search terms show up in ad reports every month.
Amazon backend keywords FAQ
What is the Amazon backend keywords limit?
249 bytes for the Search Terms attribute, generic_keywords. Amazon's help pages say it should be less than 250 bytes, and a field over the limit is ignored completely by Amazon search.
Do spaces count toward the 249 bytes?
No. Amazon states that spaces and punctuation are not counted when calculating the length of search terms.
Are backend keywords the same as Amazon search terms?
Yes. Sellers call them backend keywords; Seller Central calls the field Generic keyword, and the flat file attribute is generic_keywords.
Where do I find backend keywords in Seller Central?
Manage Products, select the product, Edit from the Fix menu, then the Generic keyword field on the Product details tab.
Should I use commas between backend keywords?
No. Separate words with spaces. Amazon recommends avoiding punctuation such as semicolons, colons and dashes.
Can I put competitor brand names in backend keywords?
No. Your own brand and other brand names are prohibited search terms, and using them can get the ASIN suppressed.
Should I include misspellings?
Amazon's current guidance says to use spelling variations but not common misspellings.
Do I need both singular and plural forms?
No. Amazon recommends using either singular or plural words.
Why are some of my search terms not working?
Amazon decides which search terms are relevant automatically and may not use all of them. Terms can also be dropped for breaking the rules, and the whole field is ignored if it is over 249 bytes.
Is the Generic keyword field required?
For most products it is optional, but since December 6, 2023, Amazon requires it for 23 product types, including board games, blankets and balloons.
How do I exclude a search term on Amazon?
Removing a word from the backend field stops it being indexed from there, but words in the title and bullets are still indexed. To stop paying for a search in ads, add it as a negative keyword in the campaign.
How often should I update backend keywords?
Review them when the search term report shows new converting terms, and whenever the title or bullets change, so nothing is repeated.
Sources
- Amazon Seller Central help, "Use search terms effectively" (US).Last verified September 17, 2026.
- Amazon Seller Central help, "Keyword attributes explained" (US).Last verified September 17, 2026.
- Amazon Seller Central help, "Optimize your product discoverability" (US).Last verified September 17, 2026.
- Amazon Seller Central help, "Product title requirements and guidelines" (US).Last verified September 17, 2026.
Want the backend field written from your own search term data?
A free audit counts the bytes, finds the repeats and prohibited terms, and lists the converting search terms your listing is missing.
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