UTM parameters
UTM / UTM tags / campaign parameters / utm_source
UTM parameters are tags added to the end of a link so analytics can record where a visit came from. Google says to always use utm_source, utm_medium and utm_campaign. Values are case sensitive, so utm_source=Google and utm_source=google are counted as two different sources.
A UTM parameter is a label you bolt onto the end of a link so that when somebody clicks it, your analytics can say where they came from. They are ordinary URL query parameters, nothing more exotic. The standard that defines that part of a web address, RFC 3986, describes the query component as beginning at the first question mark and holding non-hierarchical data alongside the path. Which is the reassuring bit: adding them does not change which page loads.
Google names three you should always use, and the wording is direct. When you add parameters to a URL, you should always use utm_source, utm_medium and utm_campaign. Source is where the click came from, medium is the kind of channel like email or cpc, campaign is the name of the push.
Two more exist from the original five, utm_term for a paid keyword and utm_content to tell similar links apart. The current Analytics documentation actually lists nine, having added utm_id, utm_source_platform, utm_creative_format and utm_marketing_tactic. Two of those nine are worth ignoring entirely, because Google says so itself: utm_creative_format and utm_marketing_tactic are not currently reported in Google Analytics properties.
Now the thing that ruins more reports than anything else here. Google states that parameter values are case sensitive, and gives its own example that utm_source=google is different from utm_source=Google. It says the same about campaign names, where SpringSale and Spring_Sale are considered distinct. Nobody notices, because both versions work perfectly. They simply arrive as two separate rows, splitting one campaign's results in half.
One curiosity worth knowing, because people state it with great confidence. UTM is usually expanded as Urchin Tracking Module, after the analytics product Google bought. Google's own archived page is titled exactly that, but the body of the same page calls the system the Urchin Traffic Monitor, and the thing it describes is a JavaScript visitor tracking module rather than the link tagging scheme. The abbreviation is older and murkier than the confident version suggests.
In practice
A team tags a newsletter with utm_source=Newsletter and the same newsletter the following month with utm_source=newsletter. Both links work. Both record visits. The report shows two sources with half the traffic each, and the monthly comparison looks like a collapse. There is no error message for this, which is why a written convention agreed once beats good intentions.
Not the same as
- Conversion tracking
- UTMs say where somebody arrived from. Conversion tracking records what they did afterwards.
- The page address itself
- They sit in the query string, so the page loads exactly as it would without them.
Why it matters to you
This is the cheapest reporting improvement available and the easiest to do inconsistently. If two people tag links without an agreed list of source and medium values, your reporting degrades quietly rather than breaking. Google also notes that missing parameters will result in not set values appearing in reporting, which is the other way this shows up.
What to ask or check
- 01Do we have a written list of the source and medium values we use?
- 02Is everything lower case, including campaign names?
- 03Are any of our links carrying parameters that Analytics does not report?
What people get wrong
That capitalisation does not matter. Google states values are case sensitive and gives its own example that utm_source=google differs from utm_source=Google, so one campaign can silently become two rows.
Red flags
- Two rows in a report that are obviously the same campaign spelled differently.
- Links tagged by several people with no written convention for source and medium.
- Not set appearing in campaign reporting, which Google attributes to missing parameters.
Where you will see it
On the end of a link after a question mark, and as traffic source, medium and campaign dimensions in Google Analytics.