Batch JSONL input format

Batch input files must be JSONL: one JSON object per line.

Request input object

Each line in the input file is a request input object:

• custom_id (string): developer-provided per-request id, must be unique
• method (string): currently only POST
• url (string): the API relative URL for the request
• body (object): the request body for that endpoint

Example (Chat Completions)

{"custom_id":"request-1","method":"POST","url":"/v1/chat/completions","body":{"model":"gpt-4o-mini","messages":[{"role":"system","content":"You are a helpful assistant."},{"role":"user","content":"What is 2+2?"}]}}

Example (Responses)

{"custom_id":"request-2","method":"POST","url":"/v1/responses","body":{"model":"gpt-4.1","input":"Tell me a short story."}}

Common pitfalls

• The file must be valid JSONL (no commas between lines).
• The file must be uploaded with purpose batch.
• Keep each line within per-request size limits and within overall batch limits.