Why consistent UTM tagging matters
GA4 treats every UTM parameter value as case-sensitive and matches on the exact string, so "Newsletter" and "newsletter" show up as two separate sources in your reports even though they are the same campaign to you. This builds a properly encoded UTM link from your inputs and flags common consistency issues - mixed casing and spaces - before you publish the link.
Why case-sensitivity causes so much quiet damage to campaign reporting
A campaign tagged "Newsletter" one month and "newsletter" the next doesn't produce an error - both links work perfectly fine for visitors - but GA4 silently reports them as two unrelated sources, splitting what should be one campaign's data across two rows and making the campaign look like it performed worse than it actually did when someone only checks one of the two variants.
Why spaces in UTM values cause a different kind of problem
A space in a UTM value gets URL-encoded into "%20" in the actual link, which is technically valid but reads as cluttered and error-prone when sharing the raw link anywhere - using an underscore or hyphen instead avoids that encoding entirely while still clearly separating words in the value.
Why Source, Medium, and Campaign Name are required but Term and Content aren't
Source, medium, and campaign name are the three parameters GA4 actually needs to attribute traffic to a specific campaign at all - term and content exist purely to add finer-grained detail (which paid keyword, which specific ad creative) on top of that baseline attribution, which is why they're useful in specific cases but not required for GA4 to track the campaign in the first place.