What is the alt text character limit on X (Twitter)?

1,000 characters — the exact limit SkedCast’s own X publishing adapter truncates against.

What is the alt text character limit on Instagram?

Meta previously enforced roughly 100 characters; that hard cutoff is widely reported (not officially confirmed by Meta) to have been lifted, so there is no confirmed technical cap today.

Does LinkedIn really allow over 4,000 characters of alt text?

The API technically allows up to 4,086, but LinkedIn’s own UI recommends well under 120 for real usability — technical ceiling and practical length are different numbers.

What happens if alt text goes over Pinterest’s limit?

Pinterest’s v5 API drops alt text over 500 characters from the Pin entirely rather than truncating it, per the adapter behavior this checker mirrors.

Is my alt text uploaded anywhere when I use this tool?

No — checking happens entirely in your browser as you type; nothing is sent to a server.

Why does the tool separate a hard limit from a "recommended" length?

A platform’s technical ceiling is often far longer than what’s actually usable for a screen-reader listener — staying under roughly 125 characters is the practical target even where the technical limit is much higher.

Free tool

Alt text character limit checker

Paste alt text and see it checked against every live platform’s real alt-text character limit at once: X and Threads at 1,000, Pinterest at 500, LinkedIn at 4,086, Bluesky at 2,000, TikTok at 300 — the exact ceilings SkedCast’s own publishing adapters enforce, plus Instagram and Facebook, which have no confirmed technical cap today.

Check your alt text character limit

Your alt text

Scanning happens in your browser — nothing is uploaded.

X (Twitter)0 / 1000
Enforced by X’s Media Metadata API — the exact ceiling SkedCast’s own X adapter truncates against.
Threads0 / 1000
Meta’s Threads publishing reference documents 1,000 characters per media child.
LinkedIn0 / 4086
LinkedIn’s Images API allows up to 4,086 characters, but LinkedIn’s own UI recommends well under 120.
Pinterest0 / 500
Pinterest’s v5 API drops alt text over 500 characters from the Pin entirely rather than truncating it.
Bluesky0 / 2000
The AT Protocol’s app.bsky.embed.images lexicon documents a 2,000-character alt field.
TikTok0 / 300
Per TikTok’s own accessibility support documentation for photo-mode alt text.
Instagram0 / no confirmed cap
Meta previously enforced ~100 characters; that hard cutoff is widely reported (not officially confirmed by Meta) to have been lifted.
Facebook0 / no confirmed cap
Meta previously enforced ~100 characters; that hard cutoff is widely reported (not officially confirmed by Meta) to have been lifted.

How to use the alt text checker

Write or paste your alt text. Describe what is actually in the image, specifically and briefly — checking happens in your browser as you type.
Read the per-platform result. Every live platform gets its own row, showing its real character limit or that it has no confirmed cap.
Fix anything over a hard limit. A red row means that platform will likely truncate or reject the alt text as written.
Trim toward the recommended length. Even under a hard limit, shorter (roughly 125 characters or less) is more usable for an actual screen-reader listener.
Paste the final text into your composer. Add it to the alt-text field your platform or scheduler provides — not the caption itself.

Worked examples

A 520-character alt text on Pinterest

Pinterest’s API drops alt text over 500 characters from the Pin entirely, so a 520-character description gets flagged as 20 characters over — and would silently disappear rather than truncate.

The same 200-character alt text on X vs. Instagram

X’s 1,000-character limit means 200 characters passes easily; Instagram has no confirmed technical cap, so the same text is never flagged there either — the difference is how each platform enforces (or doesn’t) a ceiling, not the text itself.

Alt text length checker FAQ

What is the alt text character limit on X (Twitter)?: 1,000 characters — the exact limit SkedCast’s own X publishing adapter truncates against.
What is the alt text character limit on Instagram?: Meta previously enforced roughly 100 characters; that hard cutoff is widely reported (not officially confirmed by Meta) to have been lifted, so there is no confirmed technical cap today.
Does LinkedIn really allow over 4,000 characters of alt text?: The API technically allows up to 4,086, but LinkedIn’s own UI recommends well under 120 for real usability — technical ceiling and practical length are different numbers.
What happens if alt text goes over Pinterest’s limit?: Pinterest’s v5 API drops alt text over 500 characters from the Pin entirely rather than truncating it, per the adapter behavior this checker mirrors.
Is my alt text uploaded anywhere when I use this tool?: No — checking happens entirely in your browser as you type; nothing is sent to a server.
Why does the tool separate a hard limit from a "recommended" length?: A platform’s technical ceiling is often far longer than what’s actually usable for a screen-reader listener — staying under roughly 125 characters is the practical target even where the technical limit is much higher.

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