File Too Large for ChatGPT or Claude? Shrink It on Your Mac

There are three separate limits, and only one of them is about megabytes.

A 40 MB scan with 12 pages is a size problem. A 2 MB contract with 600 pages is a length problem. Check the file size in Finder (Get Info, or press Space for Quick Look) and the page count in Preview before you do anything. If you are unsure how to read a file size, our guide to PDFs that are too big to upload covers the general case.

Anthropic’s help page for uploading files lists these limits (read 8 November 2026; limits change, so check the page):

Two things follow. First, Claude reads charts and images inside a PDF only up to 100 pages. From 101 to 1,000 pages it reads text only, so a long PDF with figures loses them. Second, the 30 MB cap applies to project files, not to a normal chat upload, so a PDF that fails in a project may upload fine in a chat.

OpenAI publishes its numbers in the File Uploads FAQ. That page refused an automated fetch when we checked, so we are not repeating figures from memory. Open it and look for the per-file size cap, the image cap, and the text cap, because they differ by file type and by plan.

The practical rule matches Claude’s: a file can pass the size cap and still fail on text length. A 300-page text PDF is often small in megabytes and still too long. Shrinking will not fix that. Splitting will.

Use Preview, which is already on your Mac:

1. Open the PDF in Preview.
2. Choose File > Export…
3. Set Quartz Filter to Reduce File Size and save a copy.

On our test PDF (three pages of photographs, 3,163,546 bytes) the stock filter produced 2,151,046 bytes, about a third smaller. That is a modest cut. Preview’s filter is one fixed setting; our Preview Reduce File Size guide explains why it sometimes makes a PDF bigger. For a bigger cut, use a tool with presets. Smol’s Medium PDF preset took the same file to 146,388 bytes. That fixture is photographs with synthetic noise, so treat it as a ceiling, not a promise: PDFs made by some generators barely shrink at all. See what each PDF preset does.

Text-only PDFs are the exception. They are already small, and image compression cannot touch them. If a text PDF is too large, it is a length problem.

Split the PDF and upload the parts. In Preview, show thumbnails (View > Thumbnails), select the pages you need, and drag them to the Desktop. Preview saves them as a new PDF. For an exact range from Terminal, qpdf works if you have installed it with Homebrew:

qpdf big.pdf --pages . 1-80 -- part1.pdf
qpdf big.pdf --pages . 81-160 -- part2.pdf

Often you do not need the whole document. Send the chapter or the clauses you are asking about, and the answer gets better as well as the upload getting smaller.

For images, the limit that bites is dimensions, not bytes. Claude accepts up to 8000 x 8000 pixels per image. Resize with sips, which ships with macOS:

sips -Z 3000 photo.jpg --out photo-small.jpg

For long recordings, drop the bitrate and make the file mono before transcribing. Speech does not need stereo or 256 kbps. Our guide to audio transcription uploads covers it, and how to reduce MP3 file size on Mac shows the measured numbers.

For one PDF, use Preview or a custom Quartz filter. Both are free and fast, and neither uploads your file. If the cause is page count, no compressor helps, and qpdf or Preview does the job. Smol does not split, merge or edit PDFs.

Smol earns its $29 (once, one Mac) when you do this regularly: a folder of mixed PDFs, photos and recordings that all need to fit under an upload limit, handled in one batch from a Finder right-click, with nothing uploaded to a third party first. That matters when the file is the contract you are about to ask an AI about. See pricing, or our best PDF compressor for Mac comparison.