Key Takeaways

• Publishers should cross-verify ads.txt against sellers.json at least quarterly. SSPs change their data without notification. Regular verification catches drift before it costs revenue.
• Request non-confidential status for all your seller entries. Confidential entries hide your identity from DSPs, reducing verification scores and potentially excluding you from premium demand.
• SSPs should update sellers.json daily or in real time. Stale data creates verification failures for all publishers on the platform.
• Both parties benefit from proactive communication. When publishers notice mismatches, reporting them quickly helps the SSP maintain data quality. When SSPs make changes, notifying affected publishers prevents avoidable revenue loss.
• The trend is toward mandatory full transparency. Both publishers and SSPs that invest in sellers.json accuracy now will be best positioned as buyer requirements tighten.

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sellers.json Best Practices for Publishers and SSPs

sellers.json is one of those standards where the ideal is simple (accurate, complete, transparent data) but the reality is messy.

SSPs update at different cadences. Publishers rarely monitor. Entries go stale. Mismatches accumulate. And 24% of ads.txt entries fail sellers.json cross-verification.

The practices in this guide address both sides of the equation: what publishers should do (even though they don't control the file) and what SSPs should do (even though publisher monitoring is limited). Both parties benefit from getting this right.

Publisher Best Practices

1. Cross-Verify Quarterly at Minimum

Every three months, validate every ads.txt entry against the corresponding SSP's sellers.json. Check:

• Account ID exists in sellers.json
• seller_type matches your DIRECT/RESELLER label
• domain field matches your publisher domain (for DIRECT entries)
• Entry is non-confidential

This catches SSP-side changes that happened without your knowledge. An entry that verified in January might fail in April because the SSP reclassified your account, updated the domain field, or ran a data cleanup.

For automated cross-verification, use BeamFlow's scanner.

2. Request Non-Confidential Status

If any SSP has your entry marked as confidential (is_confidential: true), contact them and request non-confidential status. Confidential entries hide your name, domain, and seller_type from DSPs.

The impact of confidential status:

• DSPs can't fully verify your identity
• SPO algorithms may deprioritize paths through your account
• Some buyers exclude confidential sellers entirely
• Your supply chain transparency score is lower

There are very few legitimate reasons for a publisher to be listed as confidential. If the SSP defaults new accounts to confidential, explicitly request non-confidential status during onboarding.

3. Verify New SSPs at Onboarding

When you add a new SSP and create your ads.txt entry, verify within one week that:

• The SSP's sellers.json file exists and is accessible
• Your seller_id appears in the file
• The entry details (name, domain, seller_type) are correct

Don't assume that signing an SSP contract and configuring the ad server means your sellers.json entry is in place. The two processes are often disconnected.

4. Maintain SSP Contact Information

Keep a record of your account manager or support contact at each SSP. When you discover a sellers.json mismatch, you need to contact the right person quickly. Waiting days to find the right contact while your verification is broken means days of lost demand.

5. Monitor After SSP Changes

When an SSP announces a platform migration, merger, rebrand, or system update, proactively check your sellers.json entry afterward. These events frequently cause:

• Seller_id format changes
• seller_type reclassifications
• Domain field updates
• Entries being removed or consolidated

Don't wait for quarterly verification. Check immediately after any announced SSP change.

6. Report Mismatches to SSPs

When you find a mismatch, don't just fix your ads.txt to match the wrong sellers.json data. If the sellers.json data is incorrect (e.g., wrong domain, wrong seller_type), report it to the SSP. Provide:

• Your current seller_id
• The correct business name
• Your correct publisher domain
• Whether the relationship is publisher (DIRECT) or intermediary (RESELLER)
• Evidence if applicable (contract, payment records)

7. Choose SSPs With Good Transparency Practices

When evaluating SSP partners, consider their sellers.json practices:

• Do they maintain a sellers.json file? (Not all do)
• How often do they update it?
• Do they default to confidential or non-confidential?
• Do they notify publishers of changes?
• Is their sellers.json accessible and properly formatted?

SSPs with strong transparency practices are likely to provide better demand quality because buyers trust their platform more.

SSP Best Practices

1. Update sellers.json Frequently

Daily updates are ideal. Real-time updates when seller data changes are even better.

Stale sellers.json data creates verification failures for every publisher affected by the outdated entry.

At minimum, update within 24 hours of any account change (new seller, changed type, domain update).

2. Default to Non-Confidential

Unless there's a specific, documented business reason for confidentiality, all seller entries should be non-confidential. Confidential entries reduce buyer trust and publisher revenue.

If confidential status is needed temporarily (e.g., during contract negotiations), set a clear timeline for when the entry will become non-confidential.

3. Validate Data Accuracy

Implement automated checks that verify:

• seller_ids are unique and current
• Domain fields resolve to active websites
• seller_type classifications match actual account configurations
• Names match registered business entities

4. Notify Publishers of Changes

When you change a publisher's seller_type, domain, or account structure in sellers.json, notify them. A simple email saying "Your seller_type was updated from PUBLISHER to INTERMEDIARY" gives the publisher a chance to update their ads.txt and investigate if the change is incorrect.

5. Maintain File Accessibility

sellers.json must be accessible at https://ssp-domain.com/sellers.json with:

• HTTP 200 status
• Content-Type: application/json
• Valid SSL certificate
• No authentication barriers
• Response within reasonable timeouts

Large sellers.json files (100K+ entries) should be optimized for fast delivery. Consider compression (gzip) and CDN distribution.

6. Include Complete Data

Every seller entry should include all required fields:

• seller_id
• name
• domain
• seller_type

Optional but valuable fields:

• TAG-ID in the identifiers array
• contact_email for the overall file

Complete data enables the highest level of verification. Missing fields create verification gaps.

Frequently Asked Questions

As a publisher, what can I do if an SSP refuses to make my entry non-confidential?

Escalate through your account manager. If the SSP still refuses, consider whether the reduced verification and potential CPM impact justifies continuing the relationship. Document the request and refusal for your records.

How do I know if an SSP's sellers.json practices are good?

Check three things: (1) Does the file exist and load quickly? (2) Is your entry non-confidential with accurate data? (3) When you requested a change in the past, how quickly did they respond? These three data points tell you most of what you need to know.

Should SSPs include inactive sellers in sellers.json?

No. Inactive seller entries should be removed. Stale entries in sellers.json create confusion and can be exploited by bad actors. Only active, current sellers should be listed.

What is the most impactful practice for publishers?

Quarterly cross-verification. Most publishers who start monitoring sellers.json discover mismatches they didn't know existed. Fixing those mismatches is the fastest path to recovering lost demand.