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Amazon Backend Search Terms: 249-Byte Rules and Examples
Amazon backend search terms are hidden keywords you add in the Search Terms field (called generic_keyword in listing files) to help your product show up for searches your visible listing does not cover. In the US, the field must stay under 250 bytes, which means 249 bytes is the practical maximum. Use single spaces, no punctuation, no repeats of words already on your listing, and no brand names or ASINs.
Key takeaways
- Limit: under 250 bytes in the US. Plain letters, numbers and spaces are one byte each.
- Going over the limit can mean the whole field is ignored, not just the extra words.
- Use it for synonyms, alternate names, abbreviations and use cases that are not in your title, Item Highlights or bullets.
- Never include other brand names, ASINs, subjective claims ("best") or temporary words ("new", "on sale").
- With titles now capped at 75 characters, the backend field matters more for the words that got cut.
Why backend search terms matter more in 2026
Since 27 July 2026, Amazon product titles are limited to 75 characters in all categories except media. Amazon added a 125-character Item Highlights field next to the title, but many words that used to sit in long titles now have nowhere visible to go.
Those words are not lost. Synonyms, alternate spellings and secondary phrases can move to the backend Search Terms field. Read our guide to Amazon product title requirements for how to split content between the title, Item Highlights and backend.
The rules
The byte limit
Amazon measures this field in bytes, not characters.
| Character type | Bytes each | Example |
|---|---|---|
| English letters a–z, digits 0–9 | 1 | "spatula" = 7 bytes |
| Space | 1 | — |
| Accented letters (á, é, ñ, ü) | 2 | "espátula de silicona" = 21 bytes for 20 characters |
| Euro sign and many symbols | 3 | "€" = 3 bytes |
| Emoji | 4 | Don't use them |
Amazon staff on the Seller Forums describe the limit as staying within 250 bytes. Third-party guides often say spaces and punctuation are not counted. Don't rely on that. Count the whole string, spaces included, and keep it at 249 bytes or less. That way the field is safe no matter how Amazon counts.
What happens over the limit
An Amazon staff post states that a Search Terms value over the limit is completely ignored by Amazon search. When you save in Seller Central, the editor may also trim your entry to the first 249 bytes. Neither outcome is good. An over-limit field can mean your carefully chosen keywords are not indexed at all.
Other marketplaces use different limits (Japan and India differ, for example). Check the field help in each store you sell in.
What to include
- Synonyms: "rubber scraper" for a silicone spatula, "sneakers" for running shoes.
- Alternate names and slang: "spoonula", "hoodie" vs "sweatshirt".
- Spelling variants: "gray" and "grey", "color" and "colour". Amazon search already corrects common misspellings, so skip deliberate typos.
- Abbreviations: "bpa", "usb c", "led".
- Use cases and audiences: "baker gift", "dorm", "camping", if they are true for your product.
- Either singular or plural, not both. Amazon's guidance says one form is enough.
What not to include
| Don't include | Why |
|---|---|
| Other brand names (competitors or your own) | Prohibited; can lead to suppression or account action. Your brand is already indexed from the Brand field. |
| ASINs | Prohibited and useless for matching |
| Words already in title, Item Highlights or bullets | Already indexed; wastes bytes |
| Subjective claims: best, cheapest, amazing | Not allowed |
| Temporary words: new, on sale now, limited time | Not allowed |
| Offensive or abusive terms | Not allowed |
| Punctuation: commas, semicolons, dashes | Adds nothing |
| Stop words: a, an, and, by, for, of, the, with | Adds nothing |
| Repeated words or phrases in different orders | Word order matters little; one copy is enough |
Write in lowercase. Search terms are not case-sensitive.
How to write backend search terms, step by step
Step 1: Collect your candidate keywords
Pull keywords from three places:
- Your search term report. Customer search terms that already produced clicks and orders through your ads are the best evidence you have. Export the Sponsored Products search term report from the Ads console (Reports > Create report > Sponsored Products > Search term). The console only keeps roughly the last two months of search term data, so download it regularly. The free Search Term Report Analyzer groups the converting terms for you.
- Search Query Performance (SQP). In Seller Central, Brand Analytics shows the queries that lead shoppers to your ASIN. Our guide to the Search Query Performance report explains how to read it.
- Competitor listings and keyword tools. Note the phrases top competitors use, then strip out their brand names.
Step 2: Remove what is already indexed
Write out every word in your title, Item Highlights, bullets and brand field. Cross off any candidate word that already appears. Amazon indexes individual words, so if "silicone" and "set" are in your title, you do not need "silicone set" in the backend.
Step 3: Break phrases into unique words
Backend matching works on words, not exact phrases. "cake batter spatula" and "spatula for cake batter" need only "cake batter" once, because "spatula" is already in your title.
Step 4: Rank and fill the space
Order words by relevance and search volume. Add them until you are close to 249 bytes. Stop if you are reaching for weak or loosely related terms. Irrelevant traffic does not convert, and poor conversion can hurt your ranking for the terms that matter.
Step 5: Count bytes, then save
Paste the string into a byte counter, or use a spreadsheet. In Google Sheets, =LENB(A2) counts bytes. In Excel, =LEN(A2) counts characters; use a byte counter if your string has accents or symbols.
To edit in Seller Central: Inventory > Manage All Inventory > Edit on the product, then find Search Terms in the keywords section of the listing form. For bulk updates, use the generic_keyword column in a listing template.
Worked example
Take a fictional silicone spatula set with this title (70 characters):
Brightlume Silicone Spatula Set, 3-Piece, Heat Resistant to 600F, Gray
And this Item Highlights line:
Stainless steel core, non-stick safe, for cooking, baking, mixing and scraping bowls
A bad backend entry (98 bytes):
best silicone spatula set, NEW!!, cheap OXO alternative, B0XXXXXXXX, spatulas, spatula, great gift
Problems: "best", "cheap", "great" and "new" are subjective or temporary. "OXO" is another brand. An ASIN is included. "Silicone", "spatula" and "set" repeat the title. "Spatulas" and "spatula" are both forms of the same word. Commas and exclamation marks waste bytes.
A good backend entry (150 bytes):
rubber scraper spoonula jar spreader cake batter frosting icing turner cookware utensil dishwasher bpa free nonstick pan baker gift heatproof flexible
Every word is new to the listing. It covers synonyms (rubber scraper, spoonula, turner), use cases (jar, cake batter, frosting, icing), features buyers search for (dishwasher, bpa free) and an audience (baker gift). It still leaves about 99 bytes for more terms as your search term data grows. Only list features that are true; "dishwasher" and "bpa free" must match the product.
How to check your backend terms are indexed
A common check is to search Amazon for your ASIN plus a backend keyword, for example B0XXXXXXXX spoonula. If your product appears, the word is likely indexed for that ASIN. This method is not officially supported and is not always reliable, so treat it as a rough check.
Better evidence is performance. After you update the field, watch your search term report and SQP over the next few weeks. New terms that start showing impressions and clicks confirm the change is working.
If several terms don't index:
- Check the byte count again. An over-limit field can be ignored entirely.
- Make sure the listing saved without errors in Manage All Inventory.
- Confirm none of the words are restricted terms.
Backend terms and AI shopping
Amazon's AI shopping assistant, Alexa for Shopping (which replaced Rufus on 13 May 2026), answers shopper questions using your detail page, reviews and structured product attributes. Backend search terms help keyword matching, but they are not shown to shoppers. Don't hide important product facts in the backend. If a shopper would want to know it, put it in the title, Item Highlights, bullets, or the matching product attribute. Our guide to Amazon listing optimization covers how all these fields fit together.
Common mistakes
- Going over 249 bytes with accented words or symbols you did not count.
- Repeating title words, which was common when titles were 200 characters and is still common in old listings.
- Adding competitor brands "because everyone does it". It is a policy violation.
- Never updating the field. Your search term report changes as you advertise. Review the backend every quarter.
- Leaving it empty on child variations. Each child ASIN has its own Search Terms field. Fill it with variation-specific words such as color names or sizes not in the child title.
Bottom line
Keep the Search Terms field under 250 bytes, counting every space, and fill it only with relevant words that do not already appear on your listing. Use your search term report and SQP data to choose those words. With titles cut to 75 characters, the backend is where many useful synonyms now live, so review it every time you rewrite a title.
Frequently asked questions
How many characters can I use in Amazon backend search terms?
In the US the Search Terms field must stay under 250 bytes, so 249 bytes is the practical maximum. Plain English letters, numbers and spaces are one byte each, so that is roughly 249 characters. Accented letters and symbols use two to four bytes each, which shrinks the space.
What happens if my backend search terms are over 249 bytes?
Amazon staff have said a Search Terms value over the limit is ignored by Amazon search, which means none of it may be indexed. The listing editor may also cut the text at 249 bytes when you save. Either way, keep the full field under the limit, counting spaces.
Should I put competitor brand names in backend search terms?
No. Amazon prohibits other brand names in search terms, and using them can lead to listing suppression or account action. Target competitor brands with Sponsored Products keyword or product targeting instead, where it is allowed.
Do I need commas between backend keywords?
No. Separate words with single spaces. Punctuation like commas and semicolons adds nothing for search and only uses space. Word order matters little, so you do not need to repeat phrases in different orders.
Should I repeat title keywords in backend search terms?
No. Words already in your title, Item Highlights, bullets or brand field are indexed already. Repeating them wastes bytes. Use the backend for synonyms, alternate names and terms that do not fit naturally on the visible page.
Do backend search terms matter for Alexa for Shopping and AI search?
Backend terms still help Amazon match your product to keyword searches. Amazon's AI shopping assistant, Alexa for Shopping (which replaced Rufus on 13 May 2026), leans heavily on your visible content, reviews and structured attributes, so backend terms should support a strong visible listing, not replace it.
Amazon fees, policies and features change often. Figures here were checked in October 2026; confirm current rates in Seller Central before making pricing or budget decisions. Sotrics is not affiliated with Amazon.