Bulk ad uploads fail on the whole file, not the offending row. One headline over the limit and the entire batch bounces back with an error naming a line number.
Filter before uploading
Remove anything over the platform's limit and upload the clean set. The rejected entries become a separate rewrite list rather than a blocked upload.
Rewrite rather than truncate
Cutting a headline at the character limit produces a sentence that stops mid-thought. The rewrite has to say the same thing in fewer words, which is editorial work — no automated trim substitutes for it.
Leave margin
Sitting exactly at the limit is fragile. Dynamic insertion, a currency symbol or a longer product name in a variant can push it over after approval. A few characters of headroom avoids a second rejection cycle.
Try it: Remove Lines Longer Than on SeoWolf's Notepad.