FreeurlIf you have ever stared at a UTM form wondering what goes in which box, here is the short version. utm_source is the specific place the click came from. utm_medium is the type of channel that carried it. So "newsletter" or "instagram" is a source, and "email" or "social" is a medium.
That is the whole answer to what is the difference between utm source and utm medium. The rest of this post shows how to fill both in so your Google Analytics reports stay clean, with examples you can copy.
The one-sentence rule: source is who, medium is how
Think of a postal letter. The source is the sender: "Aunt Maria." The medium is the delivery method: "airmail" or "hand-delivered." Two letters can share a sender and use different methods, and two methods can carry letters from many senders.
UTM tags work the same way. Google's own help page lists utm_source as the referrer, with examples like google, newsletter4 and billboard. It lists utm_medium as the marketing medium, with examples like cpc, banner and email. You can read the full list in Google's guide to campaign URLs.
Examples of utm_source and utm_medium side by side
This table shows how common situations map to the two fields. The source changes with the specific place. The medium stays the same across places of the same type.
| Where the link lives | utm_source | utm_medium |
|---|---|---|
| Your weekly email | weekly_digest | |
| Instagram bio link | social | |
| Facebook post you did not pay to boost | social | |
| Facebook ad | paid_social | |
| Google Ads search campaign | cpc | |
| A partner's blog post | partner_blog | referral |
| QR code on a flyer | flyer_main_street | qr |
Notice that Facebook appears twice with the same source and a different medium. That is the point of having two fields. In reports you can ask "how did Facebook do overall?" (group by source) and also "how did paid social do compared with email?" (group by medium).
Why the medium matters more than most people think
Google Analytics 4 uses the medium, along with the source, to sort your traffic into channels such as Email, Organic Social, Paid Social and Referral. Google documents these rules in its default channel group article. A few of them are worth knowing:
- Email: the medium is "email," "e-mail," "e_mail" or "e mail."
- Organic Social: the source is a known social site, or the medium is something like "social," "social-network," "social-media," "sm," "social network" or "social media."
- Paid Social and Paid Search: the source must be a known social or search site, and the medium must be "cp," "ppc," "retargeting," or start with "paid."
- Referral: the medium is "referral," "app" or "link."
If your medium does not match any rule, the visit lands in Unassigned. That is the most common reason people say "my email traffic is missing." They typed utm_medium=newsletter, and Google had no rule for it.
So the medium is not a free-text field in practice. Pick from a short list of values that Google already recognizes, and keep the creative naming for the source and campaign.
What goes in utm_source when you have many senders?
Be specific, but not so specific that you create hundreds of values. A good test: would you ever want a report line for this exact name? If yes, use it as a source.
For email, "email" alone is too vague as a source if you run a newsletter and a welcome series. Use newsletter and welcome_series, and put email in the medium. For social, the platform name works: instagram, linkedin, tiktok. For a flyer or sticker, name the placement, such as flyer_farmers_market.
Use the campaign field for the "why," like spring_sale. If you want the full picture of all five tags, our plain-English guide to UTM parameters covers them one by one.
A worked example: one product launch, four links
Say you sell handmade candles and you are launching a fall collection on https://example.com/fall. You will share it in your email list, on Instagram, in a paid Facebook ad, and on a flyer with a QR code. Here is how the tags look.
Email: ?utm_source=newsletter&utm_medium=email&utm_campaign=fall_launch
Instagram bio: ?utm_source=instagram&utm_medium=social&utm_campaign=fall_launch
Facebook ad: ?utm_source=facebook&utm_medium=paid_social&utm_campaign=fall_launch
Flyer QR code: ?utm_source=flyer_main_street&utm_medium=qr&utm_campaign=fall_launch
The campaign is identical in all four, so one report line shows the whole launch. The medium splits the launch into email, social, paid and print. The source tells you which specific placement did the work.
One honest note: "qr" is not in Google's default channel rules, so those visits will show up as Unassigned in the default channel report. They still appear correctly in the source/medium report, which is where you should look for custom values like this. If you want QR visits in a named channel, you would set up a custom channel group in Analytics.
How to build these links without typos
Typing tags by hand is where most mistakes happen. One missing ampersand and everything after it is ignored. The Freeurl UTM builder is a free tool that needs no account. Paste your page address, fill in source, medium and campaign (all three are required in the form), and copy the finished link.
- Open the UTM builder and paste your page URL.
- Pick a preset such as Email or Instagram if one fits. It fills in a source and medium for you, and you can change them.
- Type your campaign name, for example
fall_launch. - Add term or content only if you need them. Content is handy when two links in the same email go to the same page.
- Copy the link, or use the shorten button to turn it into a short link.
The builder lowercases your tags automatically. That matters because UTM values are case sensitive: Facebook and facebook show up as two different rows, as Google notes in its guide.
Should you shorten a link that has UTM tags?
Usually yes. A tagged URL can run over 150 characters and looks messy in a post, a text message or a printed QR code. A short link hides that clutter, and the tags still travel with the click to your site. If you are new to short links, see how to shorten a URL for free.
The trade-off: the short link hides the tags from the person clicking, so keep a record of what each one means. A simple spreadsheet with the short link, source, medium and campaign is enough.
Common mistakes with source and medium
Putting the platform in both fields
Writing utm_source=email&utm_medium=email tells you nothing about which email. Make the source the specific list or send.
Mixing spellings
"Email," "Email " and "e-mail" create separate rows or fail to group. Pick one spelling, write it down and reuse it.
Tagging your own internal links
Avoid adding UTM tags to links between pages on your own site. A tagged internal click can start a new session and replace the original source, so the real origin of the visit gets lost. Use tags only on links that bring people from outside.
Leaving out the campaign
Google says to include source, medium and campaign whenever you tag a URL. Missing values show up as "(not set)" in reports.
When UTM tags are not the right tool
UTM tags only work if the click lands on a site where you run Google Analytics (or another tool that reads them). If you send people to a page you do not control, such as a marketplace listing, the tags do nothing for you. In that case, a short link with its own click count is a better measure. Also, tags do not track people after they leave your page, and they cannot tell you why someone did not click.
FAQ
Quick answers to the questions people ask most about utm_source and utm_medium are below.
Frequently asked questions
Is utm_source or utm_medium more important?
Both are needed, along with utm_campaign. Google recommends always including source, medium and campaign. In practice the medium has a bigger effect on reports, because Google Analytics uses it to sort visits into channels like Email, Organic Social and Paid Social.
Can utm_source and utm_medium have the same value?
They can, but it is rarely useful. For example, source=email and medium=email does not tell you which email drove the click. Use a specific source like newsletter and keep email as the medium.
What utm_medium should I use for social media?
Use social for unpaid posts and a value starting with paid, such as paid_social, for ads. Google's default channel rules recognize both patterns when the source is a known social site.
Are UTM values case sensitive?
Yes. Google states that parameter values are case sensitive, so utm_source=Facebook and utm_source=facebook appear as separate rows. Use lowercase everywhere. The Freeurl UTM builder lowercases tags for you.