EarlyTerms

VastLint

Validating · Emerged · 57 days old · Last reviewed

VastLint is an open-source linter for VAST (Video Ad Serving Template) XML — the IAB standard that delivers video ads to web, mobile, and CTV players. It validates tags against 108 rules spanning VAST 2.0 through 4.3, surfacing missing fields, malformed URLs, and spec violations as inline squiggles inside the editor.

Built by Aleksander Sekowski with a first GitHub push on April 3 and a Show HN launch on April 20, 2026, VastLint ships one 108-rule Rust engine compiled to WebAssembly and fans out to a VS Code extension, Open VSX (Cursor, Windsurf, Kiro), a Homebrew CLI, a REST API, Go and JS bindings, plus an MCP server for AI agents — all Apache 2.0, local-first, no paywall.

💡

A trafficker writes a VAST 4.1 wrapper in VS Code. VastLint flags VAST-2.0-mediafile-https (HTTP MediaFile on an HTTPS page), VAST-4.1-vpaid-apiframework (deprecated VPAID), and a duplicate Impression URL — all before the tag hits QA or a partner ad server.

ESLint for the 200-page IAB video-ad spec — squiggles on broken tags as you type, not three weeks later in a discrepancy report.

Search Interest

peak 0
updated 2026-06-12
0 0 0
2026-05-14 2026-05-29 2026-06-12
Term Lifecycle
  1. Nascent
    0–7 days
  2. Emergent
    8–30 days
  3. Validating ← now
    31–90 days
  4. Rising
    91–180 days
  5. Established
    180 days +

Why is it emerging now?

TL;DR

VAST has been the IAB standard for 20 years and carries ~$30B of US video ad spend, but broken tags still get caught in QA or three weeks later in discrepancy reports. VastLint is the first open-source, IDE-native linter covering all 108 rules from VAST 2.0 to 4.3, shipped April 20 to VS Code, Cursor, Windsurf, and Kiro.

5 forces driving coverage — scroll →
Y Hacker News
Show HN: Vastlint, inline linting for ad tags in VS Code, Kiro, Cursor
Author: 'US video ad market is around $30B a year and a lot of that leaks through errors that are honestly pretty easy to prevent.'
Apr 20, 2026
DEV Community
I Built a VS Code Extension That Validates VAST XML as You Type
Under-100-microsecond validation on real-world CTV tags; Rust core with 108 rules covering VAST 2.0-4.3.
Apr 20, 2026
aleksUIX/vastlint
Open-source VAST XML validator (Rust + WASM)
Apr 3, 2026 Apache 2.0 · Rust · WASM
vastlint.org
Free VAST XML Validator — vastlint
Web validator, CLI, REST API, VS Code extension, Chrome extension (in review), MCP server for AI agents. No account, no rate limits, no paywall.
Visual Studio Marketplace
vastlint — VAST XML Validator
Shipped to VS Code Marketplace and Open VSX, so it runs unchanged in Cursor, Windsurf, Kiro, VSCodium, Gitpod, and Theia.

Outlook

6-month signal projection and commercial timeline.

Signal low
Revenue weak

Niche ad-ops tool; growth capped by VAST's small developer surface unless an SSP/DSP adopts it as a gate.

Risk · VAST itself is slowly being pressured by SIMID, OM SDK, and server-side ad insertion — the addressable market is shrinking, not growing.

Analogs · htmlhint · stylelint · prebid.js

Monetization timeline
  1. now
    Free OSS, zero paid SERP

    Apache 2.0, no paywall. Author monetizes via REST API on RapidAPI only.

  2. 3-6mo
    MCP + CI niche

    MCP server and GitHub Action for pre-merge VAST checks are plausible thin-SaaS wrappers.

  3. 6-12mo
    Ad-ops SaaS squeeze

    Incumbents (Google Ad Manager, Magnite, FreeWheel) may absorb the rule set into native QA.

Competition & Opportunity for term “VastLint” Placeholder

Needs at least one tracked query to compute — run enrich-trends or enrich-autocomplete to populate.

Content Gap
SERP dominated by X vs underserved queries
Revenue Potential
CPC range, affiliate availability, paid-platform count
Build Difficulty
Time-to-MVP, required integrations, incumbent lock-in

Ideas for term “VastLint”

Buildable pitches — turn this term into an article, site, product, post, newsletter, video, or course. Steal any card and run with it.

Article
VastLint vs IAB VAST Validator vs Google's VAST Inspector — which catches which errors?

Three-way comparison table against the two incumbent web validators (JW Player and Google DV360's built-in checker). Screenshots of the same broken tag in each. Zero comparison content exists today.

Article
Every VAST 4.3 rule VastLint checks, with a broken-tag example for each

Reference page for all 108 rules (VAST-2.0-mediafile-https, VAST-4.1-vpaid-apiframework, etc.) with minimal reproduction XML. Ranks for long-tail rule-ID queries that ad-ops engineers paste into Google.

Article
How to validate VAST tags in CI/CD before they reach ad partners

Tutorial using the CLI inside GitHub Actions and GitLab CI. Long-tail 'VAST pre-production validation' has no existing guide that isn't vendor-locked.

Product
vastlint-action — GitHub Action that fails a PR when VAST fixtures break

Ad-tech teams ship XML fixtures in monorepos. A drop-in Action wrapping the Rust binary with sensible defaults is a plausible micro-SaaS or sponsored OSS project.

Product
VAST Tag Monitor — cron-run VastLint against a partner feed, Slack on regression

Ad networks rotate tag templates weekly; a scheduled validator with diff alerts and a hosted dashboard fits a $29-99/mo SaaS niche that no current tool owns.

Post
I shipped a 108-rule linter in three weeks by writing the spec once in Rust

Technical Show-HN-style retrospective: how encoding the IAB spec in typed rules produced a core that serves CLI, WASM, VS Code, REST, and MCP from one codebase. Appeals to solo-founder devtools audience.

Post Newsletter / LinkedIn
The $30B Industry Where Nobody Lints Their Code

Video advertising moves around $30B a year through a 20-year-old XML format, and until April 2026 there was no open-source editor-native linter for it. A single Polish developer shipped one in three weeks.

Post HN / r/programming
Why a Rust linter compiled to WASM is the right architecture for domain-specific validation

VastLint publishes the same 108-rule engine as a Rust crate, a JS/WASM npm package, a Go port, a REST API, a CLI, a VS Code extension, and an MCP server. One rule file, six surfaces.

Post YouTube / Tech media
I broke 108 VAST tags on purpose. Here's what each linter caught.

Same 108 intentionally-malformed tags, run against VastLint, IAB's hosted validator, and two incumbent ad-ops tools. Score on a scoreboard.

What People Search Placeholder

Long-tail queries to rank for — SERP-verified volumes pending enrichment.

Keyword
Est. Volume
Competition
Content Type
vastlint alternatives
—
Very low
Comparison
how to use vastlint
—
Low
Tutorial
vastlint vs X
—
Medium
Comparison
vastlint pricing
—
Low
Explainer
Run make et-enrich-trends to populate real queries.

SERP of term “VastLint”

What searchers see today — organic results on top, paid ads if anyone's bidding. Ad density is a real-time commercial signal.

FAQ

What is VastLint?

VastLint is an open-source linter for VAST (Video Ad Serving Template) XML — the IAB standard that delivers video ads to web, mobile, and CTV players.

Why is VastLint emerging now?

VAST has been the IAB standard for 20 years and carries ~$30B of US video ad spend, but broken tags still get caught in QA or three weeks later in discrepancy reports. VastLint is the first open-source, IDE-native linter covering all 108 rules from VAST 2.0 to 4.3, shipped April 20 to VS Code, Cursor, Windsurf, and Kiro.

When did VastLint emerge?

Publicly emerged around 2026-04-20 (about 57 days ago as of 2026-06-16). EarlyTerms first recorded a pipeline signal on 2026-04-20.

Related Terms

Other terms in the same space — aliases, subtypes, competitors, and neighbors to explore next.

Explore next
Also mentioned
  • Part of VAST (Video Ad Serving Template)·IAB Tech Lab
  • Competitor htmlhint
  • Related SIMID·OM SDK·Prebid.js·stylelint

Sources

Primary URLs this report cites — open any to verify the claim yourself.

  1. 01 Show HN — Vastlint, inline linting for ad tags news.ycombinator.com ↗
  2. 02 DEV Community — I Built a VS Code Extension That Validates VAST XML as You Type dev.to ↗
  3. 03 GitHub — aleksUIX/vastlint github.com ↗
  4. 04 GitHub — aleksUIX/vastlint-go github.com ↗
  5. 05 vastlint.org — free VAST XML validator vastlint.org ↗
  6. 06 Visual Studio Marketplace — vastlint marketplace.visualstudio.com ↗
  7. 07 Open VSX — vastlint (Cursor/Windsurf/Kiro) open-vsx.org ↗
  8. 08 IAB Tech Lab — VAST 4.3 spec iabtechlab.com ↗