2025 update: With GA4 now standard and cross-platform attribution increasingly fragmented, I’ve added a section on why UTMs still matter and where to use them today.
UTM codes are one of those things every marketer has heard of, but half the ones I’ve worked with weren’t using them consistently (if at all). If you’ve ever sent an email newsletter and had no idea how many people actually clicked through to your site, or run a paid social campaign and couldn’t tell it apart from organic traffic in your reports, this is the fix.
In this post, I’ll explain what UTM codes do and share a few best practices for keeping your data clean and consistent over time.
What is a UTM Code?
In the simplest terms, UTM tags are extra text characters appended to the end of a URL. When a user clicks on that link, the data gets sent to Google Analytics and appears in your reports. They’re typically added to links placed on other websites and inside digital ads.
For example, if I were placing my homepage URL (www.davidgengler.com) in a Facebook ad as part of a larger branding campaign, the complete UTM-tagged URL might look like this:
www.davidgengler.com/?utm_source=facebook&utm_medium=cpc&utm_campaign=2025-branding
There are 5 UTM fields you can use on a link, with only 1 (Campaign Source) being required. The more structured your links are, the easier it is to segment reports.
Source is the only required tag. That said, for probably 90% of the campaigns I run, I’m always using Source, Medium, and Name. For campaigns where I’m doing heavy A/B testing of ad copy or creatives, I’ll add Content as well.
Google’s own Campaign URL Builder is a useful tool for building these out.
Why UTM Codes Still Matter in 2025
In the age of GA4, privacy regulations, and increasing fragmentation across platforms like TikTok, Instagram, Threads, and affiliate networks, UTM codes remain one of the simplest and most reliable ways to stitch campaign performance back together.
Even with tools like server-side tagging and enhanced conversions, UTMs still:
- Let you trace performance by creative or placement
- Enable cleaner attribution across platforms
- Improve visibility in tools like Looker Studio, Triple Whale, or custom dashboards
- Work with GA4’s event-based tracking model without modification
Don’t Use UTMs on Internal Links
Adding UTM parameters to internal site links (e.g., homepage → blog) can override the original source and break your attribution. Keep them external-only.
Where to Use UTM Codes in 2025
- Google Ads and Meta campaigns (Facebook/Instagram)
- TikTok Spark Ads
- Email campaigns (newsletters, flows)
- SMS/MMS platforms
- Affiliate placements
- Organic social with trackable CTAs
- QR codes in physical print
UTM Tagging Best Practices
If you build a consistent link tagging structure now, you’ll save yourself a lot of confusion later. As data accumulates, a messy Analytics setup compounds the problem. With client sites, cleaning this up is usually one of the first things I tackle.
Use dashes instead of underscores and spaces. Google doesn’t penalize dashes in its algorithm. Matt Cutts covered this in detail here if you want to go deeper.
Stay consistent with lowercase. This is the one I see ignored constantly.
utm_source=Facebook is different from utm_source=facebook
Both are sending traffic from Facebook, but Analytics treats them as two separate sources and gives them separate rows in your reports. Since Analytics defaults to lowercase, matching that convention prevents redundant entries.
Track your UTM links in a spreadsheet. Keep a record of past naming conventions so future campaigns stay consistent. The list of campaigns, placements, and social links grows fast, and without a reference you’ll end up with variations that are impossible to compare cleanly over time. Sam Wiltshire built a solid Google Doc version if you want a starting template.
Properly tagged UTMs give you better insight into what’s actually driving traffic and conversions. If you have questions or want help on the analytics or advertising side, reach out via the contact form on my homepage.