I helped someone else with this exact issue the other day, though the data was different (a number, not a URL):

How are you creating the ID? Your latest example is using a field reference, so my hunch is that this field is likely a formula that uses the RECORD_ID() function. However, this function can be added directly to your other formula:

"URL-String" & RECORD_ID()

If you still get the BOM, you could try wrapping one or both pieces in the TRIM() function, which is supposed to strip whitespace from the ends.

"URL-String" & TRIM(RECORD_ID())

…or…

TRIM("URL-String") & TRIM(RECORD_ID())

I'm late to the party but I'm dropping this here for anyone else who encounters this problem because I've just struggled with it for a couple of weeks now.

I came across the following on Stack Overflow:

%EF%BB%BF is an percent encoded byte sequence of ZERO WIDTH NON-BREAKING SPACE(aka BOM in UTF-16/UTF-32). In UTF-8, it's just an extra character.

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It get's introduced into Airtable automations when copy/pasting from one automation to another by highlighting an entire string of text including the variable, and then pasting that into another automation.

Doing so adds the variable plus a plain text label of the variable on a new line, plus at least one "zero width non-breaking space".

It's easy to delete the plain text label because it's visible, but the "zero width non-breaking space" (i.e. completely invisible UTF-8 character that breaks urls) is, well, invisible and not so easy to find.

It sounds like it might be introduced into other Airtable fields in a similar way.

Just delete the line with the offending url and start fresh without pasting anything and that will resolve the problem by deleting the "zero width non-breaking space" in the process.

I'm late to the party but I'm dropping this here for anyone else who encounters this problem because I've just struggled with it for a couple of weeks now.

I came across the following on Stack Overflow:

%EF%BB%BF is an percent encoded byte sequence of ZERO WIDTH NON-BREAKING SPACE(aka BOM in UTF-16/UTF-32). In UTF-8, it's just an extra character.

---

It get's introduced into Airtable automations when copy/pasting from one automation to another by highlighting an entire string of text including the variable, and then pasting that into another automation.

Doing so adds the variable plus a plain text label of the variable on a new line, plus at least one "zero width non-breaking space".

It's easy to delete the plain text label because it's visible, but the "zero width non-breaking space" (i.e. completely invisible UTF-8 character that breaks urls) is, well, invisible and not so easy to find.

It sounds like it might be introduced into other Airtable fields in a similar way.

Just delete the line with the offending url and start fresh without pasting anything and that will resolve the problem by deleting the "zero width non-breaking space" in the process.