curl -X POST 'https://api.openai.com/v1/completions' \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
  "model": "example-model",
  "prompt": "This is a test."
}'

# POST /completions (OpenAI API)
Base URL: https://api.openai.com/v1
Auth: Authorization; OpenAI API key; required.
Request formats: application/json.
Last verified: 2026-10-20

> Create completion

## Critical Gotchas
* The Responses API is the primary interface for new text and tool workflows; Chat Completions remains a separate compatibility API.
* Audio transcription uploads use multipart form data rather than a JSON request body.

## cURL
curl -X POST 'https://api.openai.com/v1/completions' \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
  "model": "example-model",
  "prompt": "This is a test."
}'

## Parameters
| Name | In | Type | Required | Description |
| :--- | :--- | :--- | :--- | :--- |
| model | body | string | Yes | ID of the model to use. You can use the [List models](https://developers.open... |
| prompt | body | string | Yes | The prompt(s) to generate completions for, encoded as a string, array of stri... |
| best_of | body | integer | No | Generates `best_of` completions server-side and returns the "best" (the one w... |
| echo | body | boolean | No | Echo back the prompt in addition to the completion  |
| frequency_penalty | body | number | No | Number between -2.0 and 2.0. Positive values penalize new tokens based on the... |
| logit_bias | body | object | No | Modify the likelihood of specified tokens appearing in the completion.  Accep... |
| logprobs | body | integer | No | Include the log probabilities on the `logprobs` most likely output tokens, as... |
| max_tokens | body | integer | No | The maximum number of [tokens](https://platform.openai.com/tokenizer) that ca... |
Other params: n, presence_penalty, seed, stop, stream, stream_options, suffix, temperature, top_p, user

## Response example
{"id":"string","choices":[{}]}

---
Need an API key? Get one at https://platform.openai.com/api-keys

POST

POST /completions — OpenAI API

OpenAI API key (required); https://api.openai.com/v1

OpenAI API

Create completion

Base URL: https://api.openai.com/v1
Auth: Authorization: Bearer <OPENAI_API_KEY>
Last verified: 2026-10-20 · upstream hash matched

Actions Try in browser→

Agents: curl -H "Accept: text/markdown" this URL
→ 396 tokens · Vary: Accept

Critical gotchas

The Responses API is the primary interface for new text and tool workflows; Chat Completions remains a separate compatibility API.

Audio transcription uploads use multipart form data rather than a JSON request body.

cURL

curl -X POST 'https://api.openai.com/v1/completions' \  -H "Authorization: Bearer $OPENAI_API_KEY" \  -H 'Content-Type: application/json' \  -d '{  "model": "example-model",  "prompt": "This is a test."}'

Parameters

Name	In	Type	Required	Description
model	body	string	Yes	ID of the model to use. You can use the [List models](https://developers.openai.com/api/reference/resources/models/methods/list) API to see all of your available models, or see our [Model overview](https://developers.openai.com/api/docs/models) for descriptions of them.
prompt	body	string	Yes	The prompt(s) to generate completions for, encoded as a string, array of strings, array of tokens, or array of token arrays. Note that <\|endoftext\|> is the document separator that the model sees during training, so if a prompt is not specified the model will generate as if from the beginning of a new document.
best_of	body	integer	No	Generates `best_of` completions server-side and returns the "best" (the one with the highest log probability per token). Results cannot be streamed. When used with `n`, `best_of` controls the number of candidate completions and `n` specifies how many to return – `best_of` must be greater than `n`. Note: Because this parameter generates many completions, it can quickly consume your token quota. Use carefully and ensure that you have reasonable settings for `max_tokens` and `stop`.
echo	body	boolean	No	Echo back the prompt in addition to the completion
frequency_penalty	body	number	No	Number between -2.0 and 2.0. Positive values penalize new tokens based on their existing frequency in the text so far, decreasing the model's likelihood to repeat the same line verbatim. [See more information about frequency and presence penalties.](https://developers.openai.com/api/docs/guides/text)
logit_bias	body	object	No	Modify the likelihood of specified tokens appearing in the completion. Accepts a JSON object that maps tokens (specified by their token ID in the GPT tokenizer) to an associated bias value from -100 to 100. You can use this [tokenizer tool](https://platform.openai.com/tokenizer?view=bpe) to convert text to token IDs. Mathematically, the bias is added to the logits generated by the model prior to sampling. The exact effect will vary per model, but values between -1 and 1 should decrease or increase likelihood of selection; values like -100 or 100 should result in a ban or exclusive selection of the relevant token. As an example, you can pass `{"50256": -100}` to prevent the <\|endoftext\|> token from being generated.
logprobs	body	integer	No	Include the log probabilities on the `logprobs` most likely output tokens, as well the chosen tokens. For example, if `logprobs` is 5, the API will return a list of the 5 most likely tokens. The API will always return the `logprob` of the sampled token, so there may be up to `logprobs+1` elements in the response. The maximum value for `logprobs` is 5.
max_tokens	body	integer	No	The maximum number of [tokens](https://platform.openai.com/tokenizer) that can be generated in the completion. The token count of your prompt plus `max_tokens` cannot exceed the model's context length. [Example Python code](https://cookbook.openai.com/examples/how_to_count_tokens_with_tiktoken) for counting tokens.
n	body	integer	No	How many completions to generate for each prompt. Note: Because this parameter generates many completions, it can quickly consume your token quota. Use carefully and ensure that you have reasonable settings for `max_tokens` and `stop`.
presence_penalty	body	number	No	Number between -2.0 and 2.0. Positive values penalize new tokens based on whether they appear in the text so far, increasing the model's likelihood to talk about new topics. [See more information about frequency and presence penalties.](https://developers.openai.com/api/docs/guides/text)
seed	body	integer	No	If specified, our system will make a best effort to sample deterministically, such that repeated requests with the same `seed` and parameters should return the same result. Determinism is not guaranteed, and you should refer to the `system_fingerprint` response parameter to monitor changes in the backend.
stop	body	string	No	Not supported with latest reasoning models `o3` and `o4-mini`. Up to 4 sequences where the API will stop generating further tokens. The returned text will not contain the stop sequence.
stream	body	boolean	No	Whether to stream back partial progress. If set, tokens will be sent as data-only [server-sent events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#Event_stream_format) as they become available, with the stream terminated by a `data: [DONE]` message. [Example Python code](https://cookbook.openai.com/examples/how_to_stream_completions).
stream_options	body	object	No	Options for streaming response. Only set this when you set `stream: true`.
suffix	body	string	No	The suffix that comes after a completion of inserted text. This parameter is only supported for `gpt-3.5-turbo-instruct`.
temperature	body	number	No	What sampling temperature to use, between 0 and 2. Higher values like 0.8 will make the output more random, while lower values like 0.2 will make it more focused and deterministic. We generally recommend altering this or `top_p` but not both.
top_p	body	number	No	An alternative to sampling with temperature, called nucleus sampling, where the model considers the results of the tokens with top_p probability mass. So 0.1 means only the tokens comprising the top 10% probability mass are considered. We generally recommend altering this or `temperature` but not both.
user	body	string	No	A unique identifier representing your end-user, which can help OpenAI to monitor and detect abuse. [Learn more](https://developers.openai.com/api/docs/guides/safety-best-practices#implement-safety-identifiers).

Response 200 OK

{
  "id": "string",
  "choices": [
    {
      "finish_reason": "stop",
      "index": 0,
      "logprobs": {
        "text_offset": [
          0
        ],
        "token_logprobs": [
          0
        ],
        "tokens": [
          "string"
        ],
        "top_logprobs": [
          {}
        ]
      },
      "text": "string"
    }
  ],
  "created": 0,
  "model": "string",
  "system_fingerprint": "string",
  "object": "text_completion",
  "usage": {
    "completion_tokens": 0,
    "prompt_tokens": 0,
    "total_tokens": 0,
    "completion_tokens_details": {
      "accepted_prediction_tokens": 0,
      "audio_tokens": 0,
      "reasoning_tokens": 0,
      "text_tokens": 0,
      "rejected_prediction_tokens": 0
    },
    "prompt_tokens_details": {
      "audio_tokens": 0,
      "cached_tokens": 0,
      "text_tokens": 0,
      "image_tokens": 0,
      "cache_write_tokens": 0
    }
  }
}

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