⚡ THE ESSENTIALS IN 20 SECONDS
- Backend keywords (the “Search Terms” field) are words you add to your product that shoppers do not see, but that help you appear in searches.
- On Amazon US the limit is under 250 bytes; if you exceed it, Amazon may not index the field. Check each marketplace’s limit.
- Use them for synonyms, variants, uses and words that do not fit in your title or bullets.
- Do not repeat title words, do not use third-party brands or ASINs, and do not waste space on commas.
IN THIS ARTICLE
Your title and bullets have limited space and must read well. But there are words shoppers use that do not fit or do not sound natural. That is what the hidden search terms field, better known as backend keywords, is for.
Backend keywords (search terms): a field in the Amazon listing, not visible to shoppers, where the seller adds relevant words that help index the product for additional searches.
The main rules
| Rule | Why |
|---|---|
| Respect the byte limit | If you exceed it, the field may not be indexed |
| Do not repeat title or bullet words | They are already indexed; you waste space |
| Separate words with spaces | Commas and punctuation are not needed |
| Do not use third-party brands | It violates Amazon policy |
| No ASINs or temporary terms | “new”, “sale”, “best seller” are not allowed |
| No need for plurals or capitals | Amazon usually recognizes common variations |
Always check Amazon’s official guide for your marketplace: limits and rules can change.
Bytes are not characters
This matters a lot if you sell in several languages: accented letters, ñ and other special characters take up 2 bytes instead of 1. A list of Spanish words can exceed the limit even with fewer than 250 characters.
| Text | Characters | Bytes |
|---|---|---|
| bottle | 6 | 6 |
| café | 4 | 5 |
| niño | 4 | 5 |
| botella térmica acero | 21 | 22 |
Use a byte counter, not a character counter, before saving.
What to include
- Synonyms: “water bottle”, “insulated bottle”, “tumbler”.
- Regional variants: words that change between countries.
- Uses and occasions: “office”, “gym”, “travel”.
- Audience: “kids”, “women”, “men” if relevant.
- Words in another language your shoppers use (for example, Spanish terms on Amazon US if your audience is Hispanic).
- Terms you found in your search reports that are not in your title.
What to avoid
- Competitor brand names.
- Offensive or misleading words.
- Temporary or subjective claims: “best”, “cheap”, “new”.
- Repeating the same word several times.
- Stuffing the field with irrelevant words to “show up in more searches”: it hurts conversion and may violate policy.
How to find the words
- Review the search term report from your automatic campaigns.
- Use Amazon Brand Analytics to see what shoppers search in your category.
- Read reviews: customers describe the product in their own words.
- Check Amazon’s autocomplete bar.
- Compare with competitors’ titles.
How to check indexing
Search Amazon for your ASIN together with the word you want to check. If your product appears, that word is indexed. If not, make sure you did not exceed the byte limit, that the field saved correctly, and wait a few hours, because changes can take time to show.
A typical case (fictional)
A water bottle brand filled its field with words already in the title and several accented Spanish words. Without noticing, it exceeded the byte limit. After removing repetition, adding regional synonyms and checking the byte count, it started appearing in searches that had previously given it zero impressions, and some became profitable keywords in its campaigns.
Every byte counts: use the field for what does not fit in your title, not to repeat it.
Backend keywords and advertising
Backend keywords help organic indexing and also the relevance of your automatic campaigns. If a word converts well in your ads and is not in your listing, add it: to the title if it is important and natural, or to the hidden field if it does not fit. That way your advertising and SEO feed each other. To see where you rank, also look at Best Seller Rank and Amazon’s Choice.
Checklist
- Byte count under the limit.
- No repeated title or bullet words.
- No third-party brands or temporary terms.
- Synonyms and regional variants included.
- Indexing checked with ASIN + word.
- Quarterly review with new search terms.
- A shared doc with the current field content for each ASIN.
Agency secrets about backend keywords
What I do on every account:
Every month, my campaigns’ best searches that are not in the listing move to the title or the hidden field.
In Spanish, checking bytes avoids the whole field going unindexed.
In products with variations, each child has its own field: use it for size- or color-specific words.
Backend keywords do not work miracles, but used well they open searches your competitors do not even know exist.
I’m Alonso Jiménez, a Retail Media account director. I manage campaigns on Amazon, Walmart, Target, Instacart and Mercado Libre every day, for brands in the US, Mexico and Latin America.
Frequently asked questions
What are backend keywords?
Hidden words in the “Search Terms” field that help index your product on Amazon.
What is the backend keyword limit?
On Amazon US it is under 250 bytes; check your marketplace’s limit.
Should I use commas?
It is not necessary: separate words with spaces.
Can I use competitor brands?
No, it violates Amazon policy.