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Stoqlab

Free tools

Check the supply chain behind any app

Four free tools for publishers, SSP and DSP teams. They run on the same crawl as Stoqlab itself, so the answers come back in a second, not after a crawl.

  • app-ads.txt checker

    Is the file there, does it parse, and does every seller account exist?

    Enter a developer website or a store link. You get the file's status, every malformed line, DIRECT and RESELLER counts, duplicates, unknown ad systems, and a sellers.json verdict per line.

    Input: Domain, App Store or Google Play link, bundle ID

  • sellers.json validator

    Check an SSP or exchange's sellers.json against the specification.

    Enter a network's domain. See seller types, the confidential share, entries without a domain, duplicate IDs and schema errors.

    Input: Network domain

  • Seller ID lookup

    Who is behind a seller ID, and which apps list it?

    Enter an ad system and a seller ID. See the sellers.json entry, how many apps declare it DIRECT or RESELLER, and whether one app authorises it.

    Input: Ad system domain + seller ID

  • schain validator

    Validate an OpenRTB SupplyChain object node by node.

    Paste the schain from a bid request. Every hop is checked against sellers.json and the publisher's app-ads.txt or ads.txt.

    Input: SupplyChain JSON

Three files, one question

Is this impression really sold by someone the app's developer authorised? The answer sits in three places. The developer's app-ads.txt lists the accounts allowed to sell the app's inventory. Each network's sellers.json says who owns those accounts. The schain in a bid request lists every account the impression passed through. The tools here check each piece, and each one against the others.

Where the answers come from

As of 10 October 2026, Stoqlab tracks 2.2M+ live apps (2M+ iOS, 250k+ Android), has checked the app-ads.txt of 500k+ developer hosts (89k+ files found) and reads the sellers.json of 1,300+ networks. The tools read those stored copies first, which is why they are fast, and show when each file was last read. The app-ads.txt checker and the sellers.json validator can also fetch a file live, within limits.

About the tools

Are the tools free?

Yes, with no sign-up. There is a fair-use limit per network, and live fetches are limited more tightly because they reach out to someone else's server.

Where does the data come from?

From our crawler, which reads the app-ads.txt behind App Store and Google Play apps and the sellers.json of the networks those files name, and keeps every change with its date. The methodology page explains how often each file is read.

Do you store what I type?

No. The tools do not save your checks or tie them to you. Results for public files are cached for up to an hour so a repeated check is fast, and a request counter per network enforces the limits.

Stoqlab

Get the full supply picture

The free tools answer one question at a time. Stoqlab tracks the app-ads.txt of over half a million apps and the sellers.json of every network they name, follows resellers four hops deep, and keeps every change with its date. Dashboard, REST API and MCP server. Access is by request.

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