When I try to upload a file to fine-tune a model I get this error message:
“There was an error uploading the file: Invalid file format for Fine-Tuning API. Must be .jsonl”
The file IS in jsonl format and I even tried uploading a file that used to work but it’s not working at the moment.
I’m using the UI do upload the document and fine-tune the model.
Same here 
. I get the exact same error:
There was an error uploading the file: Invalid file format for Fine-Tuning API. Must be .jsonl
I fixed it somehow by creating a .jsonl file using a code editor like VSCode and adding the json lines there.
I just ran into this issue and wanted to post the solution for anyone else who comes across it. I was using GPT-4o with canvas to create the training data, and then copying that data to a text editor and saving it as a JSONL. The problem is that the 4o output is formatted for human readability instead of following the correct JSONL formatting conventions. Once I asked 4o to reformat the text the upload worked correctly.
