UTM values are strings. Reporting tools may treat Facebook and facebook as different values even though people read them as the same platform.
The simple rule
Use lowercase for every source, medium, campaign, term, and content value unless your documented system requires something else.
utm_source=facebook&utm_medium=paid_social
How to repair the process
- Add approved values to a shared naming document.
- Make the lowercase rule visible to everyone creating links.
- Use a builder that normalizes values where appropriate.
- Audit existing links before launching a new campaign.
Changing future links will not rename old data, but it prevents the same reporting split from growing. Use the BestUTM builder to generate clean values by default.
Make normalization visible
Lowercasing is useful because it removes one easy source of fragmentation, but it should be part of a written convention. The team should also decide whether to use facebook, instagram, or a broader source such as meta.
The important choice is not the label itself; it is using the same label everywhere.
A repeatable review process
Review the link before publishing, immediately after it goes live, and again when the campaign report is first checked. These three moments catch different problems: naming errors, redirects or page issues, and unexpected reporting behavior.
Write down the correction instead of fixing one URL silently. A short record helps the whole team avoid repeating the same mistake in the next campaign.
Historical cleanup has limits
Analytics reports may allow grouping or filtering of old variants, but changing a report label does not change the original incoming value. Preserve the history, document the mapping, and standardize new work going forward.
The same issue appears with all platforms: LinkedIn versus linkedin, or Google versus google.