UTM builder API

Generate tagged URLs from the recommended template for any platform — and get told what's wrong with them. Free, no key, no rate limit.

Destination URL

Your tracked URL

Every platform page on this site is backed by structured data: the recommended parameters, the click-time macros, and the click-ID rule. The API serves that same data, and applies it.

Quick start

One GET request. No key, no signup, no Authorization header.

curl "https://utm.new/api/v1/build?url=https://example.com/pricing&platform=google-ads"

{
  "url": "https://example.com/pricing?utm_source=google&utm_medium=cpc&utm_campaign={campaignid}&utm_id={campaignid}&utm_term={keyword}&utm_content={adgroupid}",
  "platform": { "id": "google-ads", "name": "Google Ads", "status": "published" },
  "params": { "utm_source": "google", "utm_medium": "cpc", "...": "..." },
  "warnings": []
}

What makes this different

Concatenating query parameters is trivial. Knowing which ones will break your attribution is not. Every response carries a warnings array built from what the catalog knows about that specific platform.

curl "https://utm.new/api/v1/build?url=https://example.com&platform=meta-ads&extra.fbclid=abc123"

"warnings": [
  {
    "code": "click_id_auto_tagged",
    "severity": "warning",
    "param": "fbclid",
    "message": "Meta Ads appends fbclid to the landing URL on every ad click. Sending it yourself puts the parameter on the URL twice and the platform's own value wins — remove it."
  }
]

Warning code values are stable and safe to branch on. An empty array means the link is clean.

Code	Severity	Means
`click_id_auto_tagged`	warning	You sent a click ID the platform appends itself — it will be duplicated.
`click_id_missing`	warning	The platform does not auto-tag and you removed its click ID.
`tokens_unsupported`	warning	You used a macro on a platform that cannot substitute it.
`url_length_exceeded`	warning	The result is longer than the platform accepts.
`reserved_param_in_extra`	warning	A `utm_*` key was passed via `extra`; use `overrides`.
`platform_is_receiver`	warning	This platform reads UTMs, it doesn't send traffic.
`params_replaced`	info	Your URL already carried these params; they were replaced.
`platform_unverified`	info	Template is usable but hasn't been through editorial review.
`utm_id_unsupported`	info	The platform has no campaign ID to populate `utm_id`.
`override_not_in_template`	info	You overrode a key the template doesn't define.

Endpoints

Endpoint	Purpose
`GET /api/v1/build`	Build one tagged URL.
`POST /api/v1/build`	Structured overrides, or a batch of up to 50.
`GET /api/v1/platforms.json`	All 37 platforms.
`GET /api/v1/platforms/{id}.json`	One platform in full.
`GET /api/v1/openapi.json`	OpenAPI 3.1 spec.

Customising the template

Use override.<param> to replace a template value, and extra.<param> for anything that isn't a UTM. Setting an override to an empty string removes that parameter.

curl "https://utm.new/api/v1/build?url=https://example.com&platform=meta-ads&override.utm_campaign=spring-sale&override.utm_term=&extra.ref=newsletter"

Batch

curl -X POST https://utm.new/api/v1/build \
  -H "Content-Type: application/json" \
  -d '{
    "links": [
      { "url": "https://example.com/a", "platform": "google-ads" },
      { "url": "https://example.com/b", "platform": "reddit-ads",
        "overrides": { "utm_campaign": "launch" } }
    ]
  }'

A bad entry is reported inline rather than failing the whole batch.

Use it from an AI assistant

The OpenAPI spec at /api/v1/openapi.json is importable as a Custom GPT Action, a Claude tool, or a custom connector in Zapier, Make, and n8n. No auth to configure.

The click-ID rule

The single most common tagging mistake is adding a click ID the platform already appends. The API knows which is which.

Appends its own — don't add it

ChatGPT Ads oppref
Google Ads gclid
LinkedIn Ads li_fat_id
Meta Ads fbclid
Microsoft Ads msclkid
Pinterest Ads epik
Snapchat Ads ScCid
Taboola tblci
TikTok Ads ttclid
X / Twitter Ads twclid
YouTube Ads gclid

You must add it yourself

MGID adclid
Outbrain ob_click_id
Reddit Ads rdt_cid

Limits and stability

No authentication, no rate limit, open CORS.
31 taggable platforms; 37 in the catalog.
GET /build is deterministic and cached for 24h at the edge.
Only http and https destination URLs are accepted.
Breaking changes ship under a new version path. Recommendations themselves are content and may improve within v1 — every response carries a version so you can detect it.
Data is CC BY 4.0. Attribution appreciated, not enforced.