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+## Why
+
+> [GitHub Copilot](https://docs.github.com/en/copilot/quickstart) is free to use for
+> <strong>verified</strong> [students], [teachers], and [maintainers] of <strong>popular</strong> open source projects.
+<details>
+
+- Students and teachers: visit [Benefits for everyone at school](https://education.github.com/benefits)
+- Maintainers: check https://github.com/github-copilot/free_signup  
+  If you are not eligible, it indicates that your project needs more stars.
+</details>
+
+Even if you don't meet the eligibility criteria, the paid subscription
+([_Individual_](https://docs.github.com/en/copilot/copilot-individual/about-github-copilot-individual))
+is more affordable than [OpenAI's offering](https://chat.openai.com/#pricing).
+It costs only $10 and still provides access to [GPT-4](https://openai.com/gpt-4).
+
+> [!NOTE]
+> If the above options are not suitable for you - consider trying completely
+> free alternative: [openai-gemini](https://github.com/PublicAffairs/openai-gemini).
+
+[students]: https://github.com/pricing#i-am-a-student-can-i-get-access-to-github-copilot-for-free
+[teachers]: https://github.com/pricing#i-am-a-teacher-can-i-get-access-to-github-copilot-for-free
+[maintainers]: https://github.com/pricing#i-work-on-open-source-projects-can-i-get-access-to-github-copilot-for-free
+
+## What
+
+GitHub Copilot chat is exclusively available through selected IDEs.
+
+The `openai-github-copilot` project enables its use across a broader range of tools.
+It provides a general OpenAI-compatible API that can be deployed at no cost.  
+(However, a GitHub Copilot subscription is still required.)
+
+
+## Serverless?
+
+Although it runs in the cloud, it does not require server maintenance.
+It can be easily deployed to Cloudflare for free
+(with generous [limits](https://developers.cloudflare.com/workers/platform/limits/#worker-limits)
+suitable for personal use).
+
+> [!TIP]
+> Running the proxy endpoint locally is also an option,
+> though it's more appropriate for development use.
+
+
+## How to start
+
+First, you need to create an account on [Cloudflare](https://dash.cloudflare.com/sign-up).
+
+The simplest way to deploy is by manually pasting content of [`src/worker.mjs`](../cf-playground/src/worker.mjs)
+into https://workers.cloudflare.com/playground (see there `Deploy` button).
+
+> [!CAUTION]
+> This is a bit simplified version of the code, that does not implement token caching,
+> and lacks a "/token" page.  
+> To deploy full-featured version, please refer to the section below.
+
+
+### Advanced instructions
+
+> [!TIP]
+> If your account is new and you haven't created any workers yet, some of the links mentioned below
+> might be inaccessible. Therefore, it's recommended to create at least a "Hello World" Worker:
+> [Deploy "Hello World" script](https://dash.cloudflare.com/?to=/:account/workers-and-pages/create/workers/new).  
+> You can name it "copilot".
+
+[![Deploy to Cloudflare Workers](https://deploy.workers.cloudflare.com/button)](
+https://deploy.workers.cloudflare.com/?url=https://github.com/PublicAffairs/openai-github-copilot)
+
+After clicking this button, you'll be guided through the process of forking the repository first,
+which is necessary for continuous integration (CI).
+
+> [!WARNING]
+> The initial deployment will fail, because it requires _KV namespace_, which does not exist yet.
+
+Navigate to [Workers & Pages / KV](https://dash.cloudflare.com/?to=/:account/workers/kv/namespaces)
+and create a namespace with _"copilot-KV"_ name.
+Next, copy its _ID_, and modify the [`wrangler.toml`](wrangler.toml) file in your forked repository,
+replacing the existing `id` with your copied value.
+
+Once you push these changes, the CI will automatically deploy the repo to Cloudflare Workers,
+this time without any issues.
+
+
+### Manual deployment
+
+Instead of using the "_button-deploy_", you can also manage the project locally using the
+[Cloudflare CLI](https://developers.cloudflare.com/workers/wrangler/):
+- Create a _KV namespace_: `wrangler kv:namespace create KV`  
+  (and update `id` value in your [`wrangler.toml`](wrangler.toml) file).
+- Serve locally: `wrangler dev`
+- Deploy to Cloudlare Workers: `wrangler deploy`
+
+
+## How to use
+
+If you open your newly-deployed site in a browser, you will only see a `404 Not Found` message.
+This is expected, as the API is not designed for direct browser access.  
+To utilize it, you should enter your _API address_ and your Github Copilot _access token_
+into the corresponding fields in your software settings.
+
+> [!NOTE]
+> Not all software tools allow overriding the OpenAI endpoint, but many do
+> (however these settings can sometimes be deeply hidden).
+
+
+### API base / address / URL / ...
+
+Typically, you should specify the API base in this format:  
+`https://copilot.YOURSUBDOMAIN.workers.dev/v1`
+
+However, some software may expect it without the `/v1` ending:  
+`https://copilot.YOURSUBDOMAIN.workers.dev`
+
+The relevant field may be labeled as "_OpenAI proxy_".
+You might need to look under "_Advanced settings_" or similar sections.
+Alternatively, it could be in some config file (check the relevant documentation for details).
+
+For some command-line tools, you may need to set an environment variable, _e.g._:
+```sh
+set OPENAI_BASE_URL=https://copilot.YOURSUBDOMAIN.workers.dev/v1
+```
+_..or_:
+```sh
+set OPENAI_API_BASE=https://copilot.YOURSUBDOMAIN.workers.dev/v1
+```
+
+### API key
+
+First you need to obtain a Copilot-enabled Github _access token_ 
+(which should start either with `ghu_` or `gho_`).
+Once deployed, this project provides a "/token" web page that assists in generating such a token.  
+For alternative methods, please refer to the [`scripts`](scripts).
+
+Input this token into the "_OpenAI API key_" field in your software settings.
+Alternatively, it might be located in some config file
+(check the relevant documentation for details).
+
+For some command-line tools, you may need to set an environment variable, _e.g._:
+```sh
+set OPENAI_API_KEY=ghu_...
+```
+
+
+## Tech notes
+
+Copilot provides following endpoints:
+- `/v1/chat/completions`
+  - `tools` and other related properties are ignored.
+  - Output is post-processed in order to remove differences from OpenAI's.
+    The `model` property always appears as "gpt-4".
+- `/v1/embeddings`
+  - [`input`](https://platform.openai.com/docs/api-reference/embeddings/create#embeddings-create-input):
+    supports array of strings only
+  - `encoding_format`, `dimensions`: ignored.
+  - Output is not altered in any way, and has some minor differences from OpenAI's:
+    - no `object` property (`"object": "embedding"`)
+    - no `model` property (`"model": "text-embedding-3-small"`)
+- `/v1/models`: Copilot does not provide models list, so it was determined empirically,
+  and this API endpoint is served with `openai-github-copilot` itself.
+- `/token`: serves a Web page that allows you to obtain a Github Copilot access token.