RTBlint

OpenRTB linter. Validates OpenRTB 2.x bid requests and bid responses against versioned IAB Tech Lab spec snapshots, from 2.0 through the monthly 2.6 releases (currently up to 2.6-202606).

Website and playground: rtblint.org

What it checks

• Malformed JSON and wrong top-level shape
• Required fields, including required non-empty arrays
• Unknown objects and fields per version catalog (ext subtrees stay open)
• Type mismatches (string, integer, float, boolean, object, and array forms)
• Documented enum values, including AdCOM lists and vendor ranges (500+)
• Deprecated, moved, removed, and not-yet-available fields across versions
• Semantic rules: site/app/dooh exclusivity, imp media type presence, skippable video dependencies, duration exclusivity, seatbid/nbr presence on responses, and more
• Response markup coherence: bid.adm content vs the declared bid.mtype (native JSON encoding, VAST/DAAST roots, double-encoded payloads)
• Request/response cross-validation: with the originating request supplied, every bid's impid, mtype, adm markup, dealid, seat, and currency are checked against what the request actually offered
• JSON dialect: spec JSON types flag fields such as imp.secure and regs.coppa as integers, while the IAB OpenRTB protobuf schema declares 28 of them bool. Either encoding is correct on its own transport and wrong on the other, so the caller declares which one it meant
• Exchange profiles: documented protocol extras on top of the spec. --profile google-ab accepts at: 3 (FIXED_PRICE) and requires Imp.ext.billing_id. --profile prebid-server requires each Imp to name a bidder or stored request and refuses wseat/bseat. --profile xandr requires ext.appnexus.seller_member_id and video ext.appnexus.context. --profile magnite requires xAPI identity fields (imp.ext.rp.zone_id, site/app ext.rp.site_id, publisher.ext.rp.account_id). Business policy stays out
• Nested specs OpenRTB carries as strings or opaque ext: Native Ads 1.2 markup (imp.native.request and native bid.adm, including required-asset pairing), GPP header vs gpp_sid and TCF 2 shape, ${AUCTION_*} macros on billing and loss URLs, EID/SUA structure, SKAdNetwork ext.skadn
• Privacy signal contradictions: regs.coppa / device.lmt / device.dnt / regs.gdpr versus identifiers on the same payload, TCF Purpose 1 versus device-storage IDs, US Privacy Opt-Out Sale versus hashed EIDs, email-shaped user.id / site.page, DSA Transparency field presence. Findings describe the document. They do not state a legal conclusion.
• ARTF envelopes and mutation sets, including applying the mutations and revalidating what comes out

Every finding carries a stable rule id, a severity, a message, and a JSON path.

ARTF

ARTF, the IAB Tech Lab Agentic Real Time Framework, hands an agent an OpenRTB payload inside an RTBRequest envelope and takes back mutations: proposed changes the orchestrator may accept or reject one at a time. Nothing in the framework checks that the auction still validates once they are applied, and a mutation is only meaningful relative to the request it targets.

# The envelope, plus full OpenRTB validation of what it carries
rtblint validate --type artf-request rtb-request.json

# The mutation set against the auction it targets
rtblint validate --type artf-response --request rtb-request.json rtb-response.json

# Apply the mutations, revalidate, and report only what the mutations broke
rtblint validate --type artf-response --apply --request rtb-request.json rtb-response.json

Three passes:

• Envelope. Required members, lifecycle against the payloads actually carried, tmax plausibility for an in-auction call, originator and applicable_intents enum values, and the carried bid request and bid response validated as protobuf JSON.
• Mutations. The response id echoes the extension point request id (not the bid request id), each declared intent is in applicable_intents, the operation and payload oneof member match the intent, and every semantic path (/imp/{id}, /imp/{id}/pmp/deals/{id}, /user/data/segment, /seatbid/{seat}/bid/{id}) resolves to something the auction carries. ADJUST_DEAL_MARGIN is reported as having no OpenRTB field to write to, because it does not.
• Applied. The mutations are written in and the result revalidated, reporting the OpenRTB findings the mutations introduced with pre-existing findings filtered out. What the agent broke, not what arrived broken.

The ARTF v1.0 document and its .proto use different vocabularies for the same mutation (activateSegments and a value: {IDsPayload: ...} wrapper against ACTIVATE_SEGMENTS and top-level oneof members). Payloads written from the document are mapped and reported as artf.mutation.legacy_spec_encoding rather than dismissed as unknown.

Surfaces

OpenRTB 3.0 validates through its layered envelope: the transport objects (Openrtb, Request, Item, Deal, Source, Response, Seatbid, Bid) and the AdCOM 1.0 domain objects under item.spec (Placement), bid.media (Ad), and request.context. A 2.x payload sent to a 3.0 validator gets a migration diagnostic rather than a bare parse error. The 2.6-202204 snapshot has no extracted catalog and reports itself as unsupported instead of passing payloads silently. See ROADMAP.md for what's next and CHANGELOG.md for release history.

CLI

cargo install rtblint

rtblint validate request.json
rtblint validate --type response response.json
rtblint validate --type response --request request.json response.json
rtblint validate --version 2.5 --format json request.json
rtblint validate --dialect proto-json grpc-bid-request.json
rtblint validate --profile google-ab google-bid-request.json
rtblint validate --profile prebid-server pbs-auction.json
rtblint validate --profile xandr xandr-bid-request.json
rtblint validate --profile magnite magnite-bid-request.json
rtblint validate --resolve --cache ./supply-cache request.json
rtblint validate --summary bids.ndjson
rtblint validate --batch --summary bids.ndjson
cat request.json | rtblint validate --stdin

--request supplies the originating bid request so the response is also cross-validated against it (works with --batch too: one request, many response lines). --dialect proto-json validates a payload that came off a gRPC bidstream integration. --profile google-ab applies Google Authorized Buyers' documented protocol extras (at: 3 FIXED_PRICE, required Imp.ext.billing_id) on top of the spec. --profile prebid-server applies Prebid Server /openrtb2/auction extras (bidder or stored request on each Imp, no wseat/bseat). --profile xandr applies Microsoft Monetize extras (ext.appnexus.seller_member_id, video ext.appnexus.context). --profile magnite applies Magnite xAPI identity fields. --resolve --cache <dir> checks SupplyChain hops against sellers.json and the publisher's ads.txt / app-ads.txt from a local directory:

<dir>/sellers/<asi>/sellers.json
<dir>/ads/<site.domain>/ads.txt
<dir>/app-ads/<app.bundle>/app-ads.txt

Nothing is fetched; populate the cache yourself. --batch lints one JSON object per line from a file or stdin. --summary adds rule-frequency totals for a captured stream (--summary bids.ndjson for the histogram alone). See ARTF for --type artf-request and --type artf-response.

Exit codes: 0 valid, 1 validation errors, 2 usage or I/O error.

GitHub Action

The Action lives in this repo. Pin a release tag so CI downloads that CLI tarball:

- uses: aleksUIX/rtblint@v0.13.0
  with:
    path: fixtures/bid-request.json
    spec-version: 2.6-202505

version selects the CLI release (auto follows the action's own v* tag). spec-version is the OpenRTB snapshot. Linux and macOS runners, x86_64 and aarch64.

Node

import { validate, validateResponse, validateResponseAgainstRequest } from "rtblint-core";

const report = validate(JSON.stringify(bidRequest), "2.6-202505");
if (!report.valid) {
  for (const issue of report.issues) {
    console.log(`[${issue.severity}] ${issue.path}: ${issue.message} (${issue.id})`);
  }
}

// Cross-validate a response against the request it answers.
const paired = validateResponseAgainstRequest(
  JSON.stringify(bidResponse),
  JSON.stringify(bidRequest)
);

For gRPC bidstream payloads and ARTF:

import {
  validateDialect,
  validateProfile,
  validateArtfRequest,
  validateArtfResponseApplied,
  protoBoolDivergences,
} from "rtblint-core";

validateDialect(JSON.stringify(bidRequest), "proto-json");
validateProfile(JSON.stringify(bidRequest), "google-ab");
validateProfile(JSON.stringify(bidRequest), "prebid-server");
validateArtfRequest(JSON.stringify(rtbRequest));