Short answer
Google Ads headlines are 30 characters and descriptions 90. SEO titles are about 60 and descriptions about 160. Instagram bios are 150, X posts 280, LinkedIn headlines 220 and Google Business posts 1,500. The free character counter on this site checks your text against all of them at once.
Free tools for this
Ads
Google Ads responsive search ads: headlines up to 30 characters, descriptions up to 90. Text over the limit is rejected.
Facebook and Instagram ads: the recommended primary text is about 125 characters before it is cut behind See more, and about 40 for the headline. Longer text still runs but gets truncated.
Search (SEO and YouTube)
Page title: about 60 characters, and meta description: about 160. These are guides, because Google cuts by pixel width and sometimes rewrites the description. Put the important words first.
YouTube titles allow 100 characters and descriptions 5,000.
Try it now: Character Counter → · LinkedIn Headline Generator →
Social
Instagram: bio 150, caption 2,200. X: 280 per post, with every link counted as 23 and most emoji as 2. LinkedIn: headline 220, About 2,600, post 3,000.
Local and shopping
Google Business Profile: posts up to 1,500 characters and the business description up to 750.
Google Shopping: product titles up to 150 characters and descriptions up to 5,000. Many places show only the first part of a title, so lead with what the product is.
Messages
A single SMS holds 160 characters of plain text. Using an emoji or a non-English character drops it to 70 per message, and longer messages are split into several.
Writing to fit
Write the full version first, then cut. Remove filler words before you remove meaning, and keep the most important words at the start, since that is the part that is always shown.
Limits change as platforms update, so check the official guidance before you run a large campaign.