Key Takeaways

• "ID Not Found" means your account ID from ads.txt doesn't exist in the SSP's sellers.json file. The SSP has no record of a seller with that ID. DSPs can't verify the authorization chain.
• This is one of the most common sellers.json verification failures. Usually from wrong account IDs, new accounts not yet added to sellers.json, or SSP platform migrations that changed ID formats.
• The impact is a complete verification failure for that SSP path. DSPs can't confirm the seller's identity, so bids through that channel get rejected or deprioritized.
• The fix depends on the cause. ID wrong? Correct it in ads.txt. SSP hasn't added you yet? Contact them. Platform migration? Get the new ID.
• This can happen suddenly. An SSP can reorganize their sellers.json anytime. An ID that was valid last month might not exist today.

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What "ID Not Found" Means in sellers.json

You scan your ads.txt entries against sellers.json and one comes back as "ID Not Found." The line looks correct. Format is right. SSP domain matches. But the account ID simply doesn't exist in the SSP's sellers.json file.

This is a hard verification failure.

When a DSP checks the SSP's sellers.json for your seller_id and gets no result, it can't verify who the seller is. The authorization chain breaks completely. The DSP has two choices: reject the bid or bid with way reduced confidence.

"ID Not Found" is different from a relationship type mismatch or a domain mismatch. Those failures mean the DSP found your entry but something doesn't match. "ID Not Found" means the DSP searched the entire sellers.json file and your ID isn't there at all.

Why Your ID Might Not Be Found

Wrong Account ID in Your ads.txt

The most common cause. The ID in your ads.txt file doesn't match the ID the SSP assigned to you. Common mistakes:

• Using a reporting ID instead of the seller ID. SSP dashboards often show multiple types of IDs: reporting IDs, API keys, integration IDs, and seller IDs. Only the seller ID (the one used in bid requests) appears in sellers.json.
• Typo or digit error. Google publisher IDs are 16 digits. One wrong digit means a completely different (or nonexistent) account.
• Legacy ID from a previous account structure. If the SSP migrated your account, your old ID may no longer exist.
• Copying from the wrong dashboard section. Some SSPs display different ID formats in different parts of their interface.

Fix: Log into the SSP's publisher dashboard. Navigate to the ads.txt section. Copy the exact ID they provide. Replace the one in your ads.txt.

New Account Not Yet Added to sellers.json

When you create a new account with an SSP, there can be a delay before they add your account to their sellers.json file. Some SSPs update sellers.json daily. Others update weekly or less frequently. During this gap, your ads.txt entry has no corresponding sellers.json record.

Fix: Wait 48-72 hours after account creation. ID still doesn't appear in sellers.json? Contact the SSP's support team and ask when your seller entry will be added.

SSP Platform Migration

SSPs occasionally migrate their platforms, merging systems, changing ID formats, or restructuring account hierarchies. During or after a migration:

• Old IDs may be deprecated
• New IDs may be assigned
• The format may change (numeric to alphanumeric, or the prefix changes)

If your SSP went through a migration and you're still using the pre-migration ID, it won't exist in the new sellers.json.

Fix: Check the SSP's documentation or contact your account manager for your current, post-migration seller ID.

SSP Acquisition or Merger

When SSP A acquires SSP B, the combined entity often consolidates sellers.json. Accounts from SSP B may be migrated to SSP A's system with new IDs. The old SSP B IDs may no longer appear anywhere.

Fix: After any SSP merger or acquisition that affects your partners, proactively verify your account ID and update your ads.txt accordingly.

The SSP Does Not Maintain sellers.json

Some smaller or regional SSPs haven't implemented sellers.json at all. If the SSP doesn't have a sellers.json file, the "ID Not Found" is technically an "entire file not found." DSPs that require sellers.json verification will skip inventory from SSPs without the file.

Fix: Contact the SSP and encourage them to implement sellers.json. In the meantime, understand that verification for this SSP path will be limited.

Confidential or Suppressed Entry

In rare cases, the SSP may have your entry but marked as confidential without including a seller_id. This is unusual (the spec requires seller_id even for confidential entries), but data inconsistencies exist in the real world.

Fix: Contact the SSP and verify your entry is correctly listed and non-confidential.

How to Diagnose "ID Not Found"

Manual Check

1. Open the SSP's sellers.json file in your browser: https://ssp-domain.com/sellers.json
2. Use Ctrl+F / Cmd+F to search for your account ID
3. No results? Try searching for partial matches (in case of format differences)
4. Compare the ID format in sellers.json entries against what you have in ads.txt

What to Look For

• ID format differences. Some SSPs use numeric IDs (12345), others use prefixed IDs (pub-1234567890123456). Your ads.txt entry must use the exact format that appears in sellers.json.
• Leading zeros. Account 001234 is different from 1234. If sellers.json uses leading zeros and your ads.txt doesn't (or vice versa), the match fails.
• Case sensitivity. While most seller IDs are case-insensitive, some SSPs use case-sensitive IDs. ABC123 and abc123 might be treated as different IDs.

Automated Check

For publishers with many SSP relationships, manual checking is a pain. BeamFlow's scanner automatically cross-references every ads.txt entry against the corresponding sellers.json and flags "ID Not Found" issues with the specific SSP and account ID that failed.

The Revenue Impact

"ID Not Found" is a complete verification failure for that SSP path. The impact depends on how big that SSP is to your revenue:

Major SSP (Google, Index Exchange, PubMatic): Your Google publisher ID is wrong? You lose all DSP-verified Google demand. For many publishers, Google represents 20-40% of total demand. The revenue impact can be $5,000-$20,000+ per month for mid-size publishers.

Secondary SSP: A missing ID for a secondary partner may cost $500-$2,000 per month. Depends on how much demand flows through that path.

Reseller path: A missing ID for a reseller has a proportionally smaller impact, but it still means that specific supply path is unverified.

The key insight: unlike a syntax error that affects one line, an "ID Not Found" error means complete demand loss through that SSP. Not reduced demand. Zero verified demand.

Frequently Asked Questions

How long does it take for a new ID to appear in sellers.json?

It varies by SSP. Major SSPs like Google typically update within 24-48 hours. Smaller SSPs may take a week or more. Your ID hasn't appeared after a week? Contact the SSP.

Can "ID Not Found" happen after months of working correctly?

Yes. SSP platform migrations, account restructuring, or database cleanups can remove or change IDs anytime. Regular monitoring catches these changes.

What if I find my ID but the format is slightly different?

ads.txt matching is exact. sellers.json has pub-1234567890123456 and your ads.txt has 1234567890123456 (missing the pub- prefix)? It's a mismatch. Update your ads.txt to use the exact format from sellers.json.

Should I remove an ads.txt entry if the ID is not found?

Not immediately. First determine why the ID isn't found. ID genuinely wrong? Correct it. SSP hasn't added you yet? Wait. SSP no longer exists? Remove the entry. Removing a valid entry is worse than keeping a temporarily unverified one.