vastlint vs AdServe VAST Inspector

Short answer

AdServe's VAST Inspector at adserve.tv accepts a VAST tag URL or raw XML, including VPAID creatives, and runs it through a player that attempts to interpret the response, play the ad, and ping the tracking URLs. Its public page advertises support for linear, wrapper, ad pod, redirects, event tracking, click tracking, and measurement reports across VAST 2.0 through 4.2. As a playback-style check, that is a solid surface.

vastlint approaches the same tag from the standards side. It validates VAST 2.0 through 4.3 against public, spec-derived rules, documents every rule with a copyable fix, separates validation, live-URL testing, and wrapper inspection into three tools, and ships the engine as a CLI, library, and MCP server for CI and server-side use.

The name overlap is worth untangling: AdServe's “inspector” is a playback inspector: it watches the ad run. vastlint's inspector is a wrapper-chain inspector: it unwraps each redirect hop and validates every response on the way to the InLine. Those are different jobs, and most broken tags need the second one first.

The fastest way to choose between them

• Use AdServe when you want to watch the ad actually play and see tracking pings fire in a browser session.
• Use AdServe when you are still maintaining legacy VPAID creatives and want a public player that will attempt to run them.
• Use vastlint when you need spec compliance with a rule ID, severity, and spec reference for every issue, including VAST 4.3, which AdServe's public page does not advertise.
• Use vastlint when the failure is inside a wrapper chain and you need to see exactly which hop breaks.
• Use vastlint when the check has to run outside a browser: CLI, CI, server-side pipelines, or AI agents via MCP.
• Use both on high-value campaigns: standards validation first, playback confirmation second.

What AdServe's inspector shows on its public surface

The public page advertises a genuinely broad playback surface: linear and wrapper handling, ad pods, redirects, event tracking, click tracking, and measurement reports, with VAST support listed for 2.0, 3.0, and 4.0 through 4.2. The player-based approach means you see real interpretation behavior: the tool tries to play the ad and fire the trackers rather than just parsing the XML.

What the public page does not surface is the layer underneath. Advertised version support stops at 4.2 rather than 4.3, there is no public rule-by-rule catalog or derivation methodology, no distinct wrapper-inspection workflow separate from playback, and no public path to embed the checks in CI or a server-side pipeline. As with most player-style testers, the public surface is the playback experience itself.

Where vastlint closes the gap

• VAST 4.3 coverage: 4.3 has no published IAB XSD, so vastlint derives its 4.3 rules from the normative spec prose and documents how.
• Public rule docs: every error links to a rule page with the reason it fires and a copyable XML fix.
• A dedicated wrapper-chain inspector: each redirect hop is fetched, parsed, and validated individually, so you see where the chain breaks instead of a single end-to-end outcome.
• VPAID handling that matches where the industry is: vastlint detects VPAID, flags it as deprecated, and routes you to the SIMID/OMID migration path rather than just playing the legacy creative.
• An embeddable engine: the same Rust core runs in the web tools, the CLI, Go and npm packages, and the MCP server, so validation is repeatable in CI and ad-serving pipelines.

When vastlint is the better first choice

• You traffic VAST 4.3 or need one consistent rule set across all six VAST versions.
• A player rejected the tag and you need the exact element and spec reference, not a playback symptom.
• The tag redirects through multiple wrappers and you need hop-by-hop visibility.
• You are migrating VPAID creatives and need deprecation detection plus a documented migration path.
• Validation must be automated: pre-traffic checks in CI, inline checks in an SSP or ad server, or agent-driven checks over MCP.

When AdServe still earns a spot in the workflow

A playback pass that pings real tracking URLs is a useful final confirmation, and AdServe's public surface covers a wide range of playback scenarios including ad pods and legacy VPAID. If your team wants to watch the creative run before sign-off, it is a reasonable place to do it.

Just keep the layers in order. A tag that plays in one public tester can still fail in stricter players, CTV SDKs, or SSAI environments because of structural issues a playback session never exposes. Validate against the published standards first, then confirm playback.