"You may only upload 1 file at a time" in ChatGPT

What this message means

The interface limits how many files attach to any one message. Exceed it and you get this wording.

On the web that ceiling is now 20 files per message, doubled from 10 on 13 February 2026. OpenAI did not say whether the mobile apps match, so a far lower ceiling on a phone is not necessarily a fault with your account. A ceiling of 1 is lower again than anything OpenAI documents, which is worth knowing before you go looking for a setting to change: there is not one.

It is easily confused with the other one, so worth separating clearly:

The first is an inconvenience. The second means you are actually blocked.

Sending them one per message

The straightforward fix, and it works fine.

Attach the first file and send it. Attach the second and send it. Everything stays in the same conversation, so ChatGPT has all of them available when you ask your question.

The better option for more than a few

Every separate upload counts against your allowance. The rolling cap is 80 files every 3 hours, and on Free it is 3 file uploads per day, so six files is six slots. On Free that is two days.

Bundling them into one text file is one upload instead of six:

for f in reports/*.txt; do echo "=== $f ==="; cat "$f"; done > bundle.txt

On Windows PowerShell:

Get-ChildItem reports\*.txt | ForEach-Object {
  "=== $($_.Name) ==="; Get-Content $_.FullName
} | Set-Content bundle.txt

The header lines matter. They tell ChatGPT where each document starts and stops, which it needs in order to answer questions about one of them rather than blending them together.

What does not work

Zipping them. ChatGPT does not unpack archives. You spend an upload and get nothing readable. Bundling into text is the version of this idea that actually works.

Uploading a folder. Not supported. Files are individual.

Retrying the multi-file attach. The per-message limit will be the same every time, and failed attempts count toward your rate cap.

When files are related, order helps

If the documents form a sequence, a contract and its amendments, chapters, versions of a draft, send them in order and say so:

These are four versions of the same document, oldest first. Once all four are here, tell me what changed between each version.

That gets you a genuinely different and more useful answer than uploading them in whatever order they happened to be in.