What are UTM parameters and how do they work?

UTM parameters are five tags you add to a link's query string — utm_source, utm_medium, utm_campaign, utm_term, and utm_content. When someone clicks the tagged link, Google Analytics reads the tags and attributes that visit to the campaign, so you can see which email, ad, or post actually drove traffic. They change nothing about the page; they only label the click.

What is the difference between utm_source and utm_medium?

utm_source is where the click comes from (the specific site or product, e.g. facebook, newsletter, google). utm_medium is the marketing channel type (e.g. email, cpc, social, referral). A common pairing is source=facebook with medium=cpc for a paid Facebook ad. GA4 reads both together to decide the channel.

Does UTM tracking still work with Google Analytics 4 (GA4)?

Yes. GA4 reads the same five utm_ parameters Universal Analytics used. What changed is how GA4 groups them: it maps your source/medium pair to a Default Channel Group using fixed rules. That is exactly what this tool predicts, so you can confirm a link lands in Email or Paid Social before you publish it.

Should UTM parameters always be lowercase?

Yes, as a rule. GA4 stores UTM values case-sensitively, so Email, email, and EMAIL become three separate rows in your reports and split your numbers. This tool's "Force lowercase + trim" option (on by default) normalises every value so your channels stay clean. Keep it consistent across every campaign.

Which utm_medium values does GA4 recognise for Paid Search, Email, and Social?

Paid Search and Paid Social need a recognised search/social source plus a medium matching the pattern ^(.*cp.*|ppc|paid.*)$ — so cpc, ppc, and paid all qualify. Email accepts email, e-mail, e_mail. Organic Social accepts social, social-network, social-media, sm. Anything else (like chat or whatsapp-only) falls into Unassigned.

Why does my Facebook ad show as Paid Social instead of Referral?

Because GA4 recognises facebook as a social source, and when the medium is a paid pattern like cpc it files the click under Paid Social — not Referral. That is correct and useful: it separates money you spent on social ads from free social referrals. This tool flags that prediction so the result is not a surprise in your reports.

What does an Unassigned channel mean and how do I fix it?

Unassigned means your source/medium pair matched none of GA4's channel rules, so GA4 cannot bucket the traffic. It usually comes from an invented medium like chat, message, or whatsapp. Fix it by using a recognised medium — referral for shared links, social for organic posts, email for newsletters, or cpc for paid ads.

Is my data safe — does this send my links anywhere?

Nothing leaves your browser. The URL is assembled and the channel predicted entirely with client-side JavaScript; there is no server call, no logging, and no link shortener in the loop. You can disconnect from the internet after the page loads and it still works.

Marketing · Analytics

UTM Builder — GA4 Channel-Aware Campaign URL Generator

Assemble a correctly-formatted UTM campaign URL and see which GA4 Default Channel Group it will land in — Email, Paid Social, Referral — before you spend ad money. Catches the uppercase typos and stray mediums that silently break your analytics. No signup, runs entirely in your browser.

By Induwara Ashinsana— Executive Director, Ryzera TechnologiesUpdated Jun 9, 2026

Build your campaign URL

GA4 channel-aware

Website URL

The full link you want to tag. Any existing query string and #fragment are kept.

Campaign sourceutm_source

Where the traffic comes from — e.g. newsletter, facebook, google.

Campaign mediumutm_medium

The marketing channel — e.g. email, cpc, social, referral.

Campaign nameutm_campaign

A name for the campaign — e.g. june_promo, builder_launch_lk.

Campaign termutm_term · optional

Optional. Paid-search keyword.

Campaign contentutm_content · optional

Optional. Distinguishes ads/links pointing to the same URL.

Quick presets

Force lowercase + trim

URL-encode values (RFC 3986)

Campaign URL

https://induwara.lk/build?utm_source=facebook&utm_medium=cpc&utm_campaign=builder_launch_lk&utm_content=video_a

Verified: re-parsed with the WHATWG URL parser, every value round-trips.

GA4 channel

Paid Social

Source "facebook" is a recognised social site AND medium "cpc" matches the paid pattern /^(.*cp.*|ppc|paid.*)$/. GA4 files paid social here, not under Referral.

Parameter breakdown

Parameter	Raw value	Written to URL
`utm_source`required	facebook	facebook
`utm_medium`required	cpc	cpc
`utm_campaign`required	builder_launch_lk	builder_launch_lk
`utm_content`	video_a	video_a

Looks good — all required parameters present, no hygiene issues.

UTM definitions follow Google's Campaign URL Builder; channel prediction follows the published GA4 Default channel group rules; encoding follows RFC 3986. Everything runs in your browser — no link is ever sent to a server.

How it works

A UTM-tagged link is just your normal URL with up to five extra query parameters appended. Google Analytics reads those parameters on arrival and attributes the visit to a campaign. This tool does two jobs: it assembles the link correctly, and it predicts the GA4 channel so you are not surprised by your own reports a week later.

Parse the base URL. The link is split into its origin, path, existing query string, and #fragmentusing the browser's standards-compliant URL parser. The fragment is held aside and re-attached last, because UTM parameters belong in the query, never the fragment (RFC 3986 §3).
Normalise.With "Force lowercase + trim" on, each value is trimmed and lower-cased. GA4 stores UTM values case-sensitively, so Email and email become two different channels in your reports — lowercasing is the recommended hygiene step.
Encode. Each value is percent-encoded for the query component per RFC 3986 §2.1/§3.4, so spaces, ampersands, and non-ASCII characters (including Sinhala and Tamil) cannot break the link. Empty optional parameters are dropped entirely.
Assemble. The UTM pairs are appended with the right separator — ? if the base URL has no query yet, & if it already does — preserving any non-UTM parameters already present. The fragment is re-attached at the end.
Cross-check.The finished string is re-parsed with the WHATWG URL parser and every value is decoded back and compared to what you typed. If they all round-trip, the link is provably well-formed — shown as the "Verified" note under the URL.

To predict the channel, the tool evaluates Google's published GA4 Default Channel Group rules in order against the lower-cased source and medium, first match wins. The key deterministic rules it implements: Paid Search (a recognised search engine plus a medium matching ^(.*cp.*|ppc|paid.*)$), Organic Search (medium = organic), Paid Social (a recognised social site plus the same paid pattern), Organic Social, Email, Affiliates, Referral, and Display. Anything that matches none of these is reported as Unassigned and flagged as a warning. The exact rule that fired is shown next to the prediction, so it is explainable rather than magic.

Worked examples

Email newsletter (normalisation)

source newsletter · medium “Email ” · campaign june_taxtips

Normalise: “Email ” → “email” (trimmed + lower-cased).
No existing query on the base URL → use “?”.
URL: …/sri-lanka-tax-calculator?utm_source=newsletter&utm_medium=email&utm_campaign=june_taxtips
Rule: medium “email” is a GA4 email value → channel Email. ✓

Facebook paid ad (the surprising one)

source facebook · medium cpc · campaign builder_launch_lk · content video_a

URL: …/build?utm_source=facebook&utm_medium=cpc&utm_campaign=builder_launch_lk&utm_content=video_a
Rule: source “facebook” is a social site AND medium “cpc” matches ^(.*cp.*|ppc|paid.*)$.
Channel: Paid Social — not Referral, which is what most people expect. ✓

Existing query + a medium GA4 won’t recognise

base …/tools?ref=card · source whatsapp · medium chat · campaign share

Base URL already has a query (ref=card) → use “&”, keep ref=card.
URL: …/tools?ref=card&utm_source=whatsapp&utm_medium=chat&utm_campaign=share
Rule: medium “chat” matches no GA4 channel pattern → Unassigned. ⚠
Fix: use medium “social” for an organic share, or “referral”. ✓

Frequently asked questions

Sources & references

The UTM definitions, GA4 channel rules, and encoding behaviour on this page were last cross-checked against the sources above on 2026-06-09. Google revises its Default Channel Group rules occasionally; this page is reviewed when they do.

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