How should I host the file?

Serve at /ads.txt (or /app-ads.txt) with Content-Type text/plain over HTTPS. Exchanges poll for changes.

Why are some of my lines flagged as unknown relationship?

Only DIRECT and RESELLER are valid. Anything else is a parse error — even typos like "Direct".

ads.txt / app-ads.txt Validator

Enter a publisher domain to fetch its ads.txt or app-ads.txt through the FizzKit relay (HTTP status, content-type, redirect chain and size are checked), or paste a file. Every record is parsed into domain, publisher ID, relationship and certification ID; duplicates, malformed lines and TAG-ID formats are flagged, and variables are validated semantically (one OWNERDOMAIN, MANAGERDOMAIN with country code, INVENTORYPARTNERDOMAIN, CONTACT, SUBDOMAIN). SUBDOMAIN= files can be fetched and merged. The Cross-check tab fetches each exchange's sellers.json and verifies that every account ID exists with a compatible seller_type. Export a canonical, deduplicated file, diff two versions, or download CSV.

Fetches URLs via the FizzKit relay — nothing is stored

For long ads.txt files, open fullscreen for a wider table

Fetch ads.txt by domain

app-ads.txt

ads.txt content

702 chars · 22 lines

2 errors, 1 warning — 1 unparseable line, 1 record error, 0 variable/semantic errors, 1 duplicate.

SUBDOMAIN pointers (1)

news.example.com/ads.txtnot fetched

Line	Exchange domain	Publisher ID	Relationship	Cert ID	Extra	Status
4	google.com	pub-1234567891234567	DIRECT	f08c47fec0942fa0	—	ok
5	google.com	pub-0987654321098765	RESELLER	f08c47fec0942fa0	—	ok
6	openx.com	123456	DIRECT	6a698e2ec38604c6	—	ok
7	openx.com	987654	RESELLER	6a698e2ec38604c6	—	ok
8	rubiconproject.com	17054	DIRECT	0bfd66d529a55807	—	ok
9	pubmatic.com	156515	DIRECT	5d62403b186f2ace	—	ok
10	indexexchange.com	189423	RESELLER	—	—	ok
11	appnexus.com	3663	DIRECT	f5ab79cb980f11d1	—	ok
12	appnexus.com	3663	DIRECT	f5ab79cb980f11d1	—	duplicate of line 11
16	google.com	pub-x	UNKNOWN_REL	—	—	Unknown relationship "UNKNOWN_REL" (expected DIRECT or RESELLER).

Records

DIRECT

RESELLER

Exchanges

Duplicates

Errors

Warnings

Subdomains

0/1

sellers.json Inspector

Fetch any exchange's sellers.json by domain, validate it against the IAB spec, cross-check a publisher's ads.txt against it, and resolve OpenRTB supply chains.

OpenRTB Inspector

Validate & annotate OpenRTB 2.6 BidRequest and BidResponse JSON.

OpenRTB Request Builder

Build OpenRTB 2.6 bid requests with a form or JSON, then send them to any bidder and inspect the response.

RTB Bidder Sandbox

A live OpenRTB bidder endpoint that captures every bid request and answers with bids, no-bids, custom templates or timeouts.

How to use ads.txt / app-ads.txt Validator

1Enter a publisher domain (or paste a file), choose ads.txt or app-ads.txt, and press Fetch.
2Review the status chips: HTTP status, text/plain content-type and redirect count are checked against the spec.
3Open Issues to see syntax errors, duplicates and variable problems; click an error to jump to the line.
4Fetch SUBDOMAIN= files to merge them, then run Cross-check to verify every line against each exchange's sellers.json.
5Download the canonical file, diff against another version, or export CSV.

About ads.txt / app-ads.txt Validator

ads.txt / app-ads.txt Validator is part of FizzKit — a collection of focused developer and ad-tech tools. This tool uses the FizzKit relay to fetch public URLs on your behalf (so browser CORS rules do not get in the way); fetched content is returned to your browser and not stored.

Frequently asked questions

Yes. The format is identical — app-ads.txt is just ads.txt served from a developer's domain for mobile apps.

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