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docs/faq.md

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 # Frequently asked questions
 
+## GPT-4 vs GPT-3.5
+
+Aider supports all of OpenAI's chat models.
+You can choose a model with the `--model` command line argument.
+For a discussion of using other non-OpenAI models, see the
+[FAQ](#can-i-use-aider-with-other-llms-local-llms-etc).
+
+You will probably get the best results with one of the GPT-4 models.
+They have large context windows, better coding skills and
+they generally obey the instructions in the system prompt.
+GPT-4 is able to structure code edits as simple "diffs"
+and use a
+[repository map](https://aider.chat/docs/ctags.html)
+to improve its ability to make changes in larger codebases.
+
+GPT-3.5 is supported more experimentally
+and is limited to editing somewhat smaller codebases.
+It is less able to follow instructions and
+can't reliably return code edits as "diffs".
+Aider disables the
+repository map
+when using GPT-3.5.
+
+For a detailed and quantitative comparison, please see the
+[code editing benchmark results for GPT-3.5 and GPT-4](https://aider.chat/docs/benchmarks.html).
+
+In practice, this means you can use aider to edit a set of source files
+that total up to the sizes below.
+Just add the specific set of files to the chat
+that are relevant to the change you are requesting.
+This minimizes your use of the context window, as well as costs.
+
+| Model             | Context<br>Size | Edit<br>Format | Max<br>File Size | Max<br>File Size | Repo<br>Map? |
+| ----------------- | -- | --     | -----| -- | -- |
+| gpt-3.5-turbo     |  4k tokens | whole file | 2k tokens | ~8k bytes | no |
+| gpt-3.5-turbo-16k | 16k tokens | whole file | 8k tokens | ~32k bytes | no |
+| gpt-4             |  8k tokens | diffs | 8k tokens | ~32k bytes | yes |
+| gpt-4-32k         | 32k tokens | diffs | 32k tokens  | ~128k bytes | yes |
+
 ## Can I use aider with other LLMs, local LLMs, etc?
 
 Aider does not officially support use with LLMs other than OpenAI's gpt-3.5-turbo and gpt-4