Key Takeaways

• "Exchange Not Found" means the SSP domain in your ads.txt doesn't have an accessible sellers.json file. The DSP tried to fetch sellers.json from that domain and got nothing.
• This can mean the domain is wrong in your ads.txt, or the SSP genuinely doesn't maintain sellers.json. Both prevent DSP verification, but they have different fixes.
• Every entry referencing that SSP is affected. Unlike "ID Not Found" which affects one entry, "Exchange Not Found" means none of your entries for that SSP can be verified through sellers.json.
• Some SSPs use different domains for their sellers.json than their brand name. The exchange domain in ads.txt must match where the SSP actually hosts their sellers.json.
• The fix is either correcting the domain or accepting limited verification for that SSP.

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What "Exchange Not Found" Means and How to Fix It

When you see "Exchange Not Found" in a sellers.json verification report, it means the first field of your ads.txt entry (the SSP's exchange domain) doesn't have an accessible sellers.json file.

The verification system tried to fetch https://ssp-domain.com/sellers.json and either got a 404, a timeout, or no sellers.json file at that domain at all.

This is a broader failure than "ID Not Found." With "ID Not Found," the SSP's sellers.json exists but your specific account isn't in it. With "Exchange Not Found," the sellers.json file itself doesn't exist at the domain you specified. Every entry in your ads.txt that references that domain is affected.

Common Causes

Wrong Exchange Domain in ads.txt

The most fixable cause. You used the SSP's brand website or marketing domain instead of their actual exchange domain.

Example mistakes:

| Wrong (in ads.txt) | Correct (in ads.txt) |

|---------------------|---------------------|

| rubiconproject.com | rubiconproject.com (actually correct) |

| pubmatic.co | pubmatic.com |

| admanager.google.com | google.com |

| xandr.com | appnexus.com |

SSPs sometimes operate under different domains for different purposes. The exchange domain that appears in bid requests and hosts sellers.json may not be the same as the company's corporate website. Xandr (now Microsoft Advertising) still uses appnexus.com as their exchange domain in many contexts.

Fix: Check the SSP's documentation for the correct exchange domain. Most SSPs provide the exact domain to use in their ads.txt entry template.

SSP Rebranded or Changed Domains

SSPs rebrand. They get acquired. They merge platforms. When this happens, the exchange domain may change. Publishers don't always get notified.

Examples from recent years:

• Rubicon Project became Magnite (but rubiconproject.com may still be the exchange domain)
• AppNexus became Xandr, then Microsoft Advertising
• Smaato was acquired by Verve Group
• MoPub was acquired by AppLovin and shut down

After a rebrand or acquisition, verify which domain the SSP currently uses for sellers.json. The answer may be the old domain, the new domain, or sometimes both during a transition period.

Fix: Check the SSP's current technical documentation or ask your account manager for the correct exchange domain.

SSP Does Not Implement sellers.json

Some SSPs, particularly smaller or regional ones, haven't implemented sellers.json. The specification is technically optional, though the industry is moving toward treating it as a requirement.

Without sellers.json, DSPs can't perform the identity verification step. They can still check ads.txt for basic authorization, but the full supply chain verification is incomplete.

Fix: This isn't something you can fix on your own. Contact the SSP and request they implement sellers.json. Major DSPs increasingly require it, so SSPs that don't implement it will lose demand over time. In the meantime, understand that inventory sold through this SSP will have lower verification scores.

sellers.json Is Hosted at a Non-Standard Path

The IAB spec says sellers.json should be at /.sellers.json or /sellers.json on the exchange domain. Some SSPs host it at a non-standard path or behind a different endpoint.

Fix: Check both https://ssp-domain.com/sellers.json and https://ssp-domain.com/.sellers.json. If neither works, the SSP may not have the file publicly accessible.

Temporary Hosting Issue

sellers.json files are hosted on web servers. Like any web resource, they can have downtime. If the SSP's server had a temporary outage or SSL certificate issue when the verification tool checked, the file would appear inaccessible.

Fix: Try again later. If the file is consistently inaccessible, the issue is likely not temporary.

How It Differs From "ID Not Found"

| Aspect | Exchange Not Found | ID Not Found |

|--------|-------------------|--------------|

| What failed | The entire sellers.json file can't be fetched | The file exists but your specific ID isn't in it |

| Scope | All entries for that SSP are affected | Only the specific entry with the wrong ID |

| Likely cause | Wrong domain or SSP has no sellers.json | Wrong account ID or new account not yet listed |

| Fix location | First field of ads.txt (exchange domain) | Second field of ads.txt (account ID) |

Impact on Your Ads

When the exchange isn't found:

All entries for that SSP fail verification. You have three entries for the same SSP (one DIRECT, two RESELLER)? All three fail because the sellers.json file can't be fetched from that domain.

DSPs vary in their response. Some DSPs will still bid based on the ads.txt check alone (basic authorization without identity verification). Others require sellers.json for full verification and will skip the inventory.

The impact depends on the SSP's market share. If the affected SSP represents 5% of your demand, the impact is limited. If it represents 30%, you have a big verification gap.

How to Diagnose

Step 1: Take the exchange domain from your ads.txt entry (first field).

Step 2: Try fetching sellers.json:

text
curl -I https://exchange-domain.com/sellers.json

Step 3: Check the response:

• HTTP 200: File exists. "Exchange Not Found" may have been a temporary issue, or the verification tool checked a different URL path.
• HTTP 404: No file at that path. The SSP either doesn't have sellers.json or hosts it elsewhere.
• SSL error: Certificate issue on the SSP's domain.
• Connection refused/timeout: Server issue on the SSP's end.

Step 4: If 404, try alternative paths:

text
curl -I https://exchange-domain.com/.sellers.json
curl -I https://www.exchange-domain.com/sellers.json

Step 5: If all paths fail, check the SSP's documentation or contact support for the correct sellers.json location.

What to Do When the SSP Has No sellers.json

If you confirm the SSP genuinely doesn't maintain sellers.json:

1. Keep the ads.txt entry. The entry still provides basic authorization that some DSPs check, even without sellers.json cross-verification.
2. Contact the SSP. Ask when they plan to implement sellers.json. Major DSP requirements are pushing all SSPs in this direction.
3. Monitor the impact. Track CPMs and fill rates from that SSP. If verified SSPs are way outperforming unverified ones, that data point supports a conversation with the SSP.
4. Consider the SSP's long-term viability. An SSP that hasn't implemented sellers.json by 2025 is behind on industry standards. This may affect their ability to attract buyer demand over time.

Frequently Asked Questions

How many SSPs still lack sellers.json?

Among major SSPs and exchanges, sellers.json adoption is near-universal. The gaps are primarily among smaller, regional, or niche SSPs. Major platforms like Google, PubMatic, Magnite, Index Exchange, and OpenX all maintain sellers.json.

Can "Exchange Not Found" resolve itself?

If the cause is temporary (server downtime, DNS issue), yes. Check again after 24-48 hours. If the cause is structural (wrong domain, no sellers.json), it won't resolve on its own.

Should I remove ads.txt entries for SSPs without sellers.json?

Not necessarily. The ads.txt entry still provides basic authorization. Only remove entries for SSPs you're no longer working with. For active SSPs without sellers.json, the entry is better than nothing while you encourage the SSP to implement the standard.

How do I find the correct exchange domain?

The most reliable source is the ads.txt entry template provided by the SSP in their publisher dashboard. The exchange domain in that template is the domain they use for bid requests and sellers.json hosting.