What is utm_source?

The short answer

utm_source is the UTM parameter that identifies the origin of a click — the specific site, platform, app or publication that sent the visitor. When someone opens https://example.com/page?utm_source=newsletter&utm_medium=email&utm_campaign=spring_sale, the analytics platform records "newsletter" as the source of that session. Everything downstream — channel grouping, campaign comparison, conversion attribution — starts from that label.

The name is literal: it is the source of the traffic. Common values are platform names (google, facebook, instagram, linkedin), owned channels (newsletter, blog), or partner names (partner_site, podcast_name). Because it is the most granular "where did this come from" label in the standard set, analytics documentation treats it as one of the three core parameters to include on every campaign URL, alongside utm_medium and utm_campaign.

utm_source vs utm_medium: the distinction that matters

Beginners most often confuse source and medium. The clean way to think about it: source names the specific origin; medium names the type of channel. utm_source=newsletter says the click came from your newsletter; utm_medium=email says the channel family was email. utm_source=instagram with utm_medium=social says the click came from Instagram, via the social channel.

This separation exists because analytics reports aggregate on medium. A short, controlled list of medium values — email, social, cpc, referral, organic — gives you clean channel-level reports, while the source dimension lets you drill into exactly which platform within that channel performed. If every link used a free-text medium, channel reporting would fragment; if every link used only a medium with no source, you could never tell Instagram apart from LinkedIn. Use both, with source specific and medium categorical.

The five standard UTM parameters

Analytics platforms recognize five standard parameters. They can appear in any order in the query string; convention usually lists them source, medium, campaign, term, content.

1. utm_source — the origin

Identifies which site sent the traffic. Examples: google, newsletter, facebook, partner_blog. Required for meaningful attribution; without it, reports cannot name the origin.

2. utm_medium — the channel type

Identifies the marketing medium: email, social, cpc, referral, banner. Keep this a short controlled list so channel reports stay readable.

3. utm_campaign — the promotion

Names the specific campaign the link belongs to: spring_sale, product_launch, weekly_digest. One campaign value can span many sources and mediums, which is how you measure a campaign's total impact.

4. utm_term — the keyword (optional)

Records the paid-search keyword that triggered an ad, e.g. utm_term=running+shoes. Mainly used in search advertising; rarely needed on organic or email links.

5. utm_content — the variant (optional)

Differentiates links that point to the same URL from the same source, e.g. hero_button versus footer_link in one email. Useful for A/B testing creatives and for telling multiple placements apart.

A real example, end to end

Say you are promoting a product page in three places: your newsletter, an Instagram post, and a Google ad. You tag each link with the same campaign but different sources and mediums:

• https://example.com/product?utm_source=newsletter&utm_medium=email&utm_campaign=spring_sale
• https://example.com/product?utm_source=instagram&utm_medium=social&utm_campaign=spring_sale
• https://example.com/product?utm_source=google&utm_medium=cpc&utm_campaign=spring_sale&utm_term=running+shoes

In your analytics, the campaign report shows spring_sale with three source/medium rows underneath — one comparable view of the whole push, with each channel's contribution visible. That is the entire point of the convention: consistent labels turn scattered links into one measurable campaign.

Where the values get read

When a tagged URL loads, the analytics software on the destination page reads the query string and stores the UTM values with that session. In Google Analytics, they populate the session's source, medium and campaign dimensions; other platforms map them to equivalent fields. The values persist for the session according to each platform's attribution rules, so a visitor who clicks a tagged link and converts later can still be credited to the original campaign. What matters on your side is only that the labels are present, spelled consistently, and unique to what they describe.