Convert images to WebP in ChatGPT
Fast WebP Converter connects to ChatGPT as an app (OpenAI also calls them plugins or connectors). Paste an image URL, a list of URLs or a page address and ask for WebP: ChatGPT calls the converter, shows the result as a card in the conversation, and hands you download links with the size before and after. The same account works in Claude, in your editor and through the API.
Set it up in ChatGPT
Until the listing is live in ChatGPT's directory, add it by address in developer mode. Four steps, the first three once.
Turn on developer mode
On chatgpt.com, open Settings, then Apps (Plugins or Apps & Connectors depending on your version), Advanced settings, and turn on Developer mode. It is available on paid ChatGPT plans; in a workspace, an admin may have to allow it.
Create the app
Press Create (or +). Name: Fast WebP Converter. MCP server URL: https://www.fastwebpconverter.com/api/mcp. Authentication: OAuth. Confirm.
Sign in
ChatGPT opens the Fast WebP Converter sign-in: use a code sent to your e-mail or Google (a free account is created if you have none), then allow ChatGPT.
Ask for WebP
In a new chat, pick Fast WebP Converter in the + menu (or mention it by name), paste the image or page URL and say what you want.
What you can ask
- “Convert https://example.com/images/hero.png to WebP at quality 80, 1600 px wide at most.”
- “Audit https://example.com and tell me how much I would save by serving its images as WebP.”
- “Convert these product photos to WebP and give me one ZIP: (paste the image URLs)”
- “Turn this animated GIF into an animated WebP: https://example.com/demo.gif”
- “Convert our logo to lossless WebP: https://example.com/logo.png”
- “How many WebP conversions do I have left this month?”
Behind the requests, ChatGPT calls the server's tools: convert_image, convert_images, audit_page, get_account, get_pricing. Each converted image counts as one conversion of your monthly allowance; audits, account and pricing questions use none.
audit_page uses no conversion, and the same audit is free on the website: paste a URL in the image audit and see each image's real WebP saving, no account needed.
Images on the web, files on your computer
The app converts images that have an address: a URL on your site, a CDN, a product feed. ChatGPT passes the address and the server fetches the image, checks it is really an image and refuses private network addresses.
For files on your computer, the browser converter is the quickest route: drop a whole folder, nothing is uploaded. Developers can also send files to the API (up to 4 MB per upload).
The WebP Converter GPT
A WebP Converter GPT for the GPT Store is on the way. Meanwhile you can build a private one for yourself or your team in five minutes: it calls the same API through a GPT action.
- In ChatGPT, open GPTs, Create, Configure, and give it a name and instructions (convert images by URL, always ask for JSON results).
- Under Actions, Create new action, Import from URL:
https://www.fastwebpconverter.com/openapi.json. - Authentication: API Key, Auth type Bearer, and paste a key from your account page.
- Save it as Only me or for your workspace. Everyone who uses that GPT spends your key's allowance, so do not publish a GPT with your own key.
App or GPT?
| ChatGPT app (MCP) | Custom GPT (action) | |
|---|---|---|
| Account | Each person signs in with their own account (OAuth) | One API key, set by whoever builds the GPT |
| Tools | All of them: convert_image, convert_images, audit_page, get_account, get_pricing | convert (by URL) and usage |
| Result | A card in the conversation with the download link | A download link in the reply |
| Where | Any chat, next to other apps | Inside that GPT only |
| Best for | Day-to-day use | A team GPT with fixed instructions |
Free and paid plans
Connecting the app is free; ChatGPT's side is your ChatGPT plan. A free Fast WebP Converter account is the way to try it: 50 conversions a month on the server, shared by Claude, ChatGPT, every MCP client and the API. Pro is full access, paid monthly, yearly or once for life ($4.99/month, $29/year or $59 once), with 10,000 server conversions a month (fair use). The monthly allowance resets on the 1st (UTC).
What each plan allows on the server (API, Claude, ChatGPT, MCP clients)
| Plan | Price | Server conversions | Images per batch call | Image by URL up to | API requests a minute | Download links kept |
|---|---|---|---|---|---|---|
| Free | Free | 50 a month | 5 | 10 MB | 10 | 24 hours |
| Pro | $4.99/month, $29/year or $59 once | 10,000 a month | 50 | 25 MB | 120 | 3 days |
Cancel anytime from your account. 14-day money-back guarantee.
What ChatGPT and Fast WebP Converter see
The assistant sends Fast WebP Converter only what a tool needs: the image URL or image data, the options (quality, maximum width, lossless) and, for an audit, the page address. It never sees the rest of the conversation. Originals are processed in memory and not kept; converted files stay behind an unguessable download link for 24 hours on Free (3 days on Pro), then they are deleted. Details in the privacy policy.
The browser converter on the home page is still the private option for files on your computer: it encodes on your device and uploads nothing.
Questions
ChatGPT can explain WebP and sometimes convert a file with its code tool, but it cannot fetch the images of your website, batch them into one ZIP or tell you what a page would save. With the Fast WebP Converter app it calls a real encoder (libwebp) on the server and returns download links with the size before and after.
Turn on developer mode (Settings, Apps, Advanced settings), press Create, name it Fast WebP Converter, paste https://www.fastwebpconverter.com/api/mcp as the MCP server URL with OAuth, then sign in with an e-mail code or Google and allow ChatGPT.
Developer mode, the manual route, is on paid ChatGPT plans on the web (Plus, Pro, Business, Enterprise and Edu at the time of writing); in a workspace an admin decides whether custom apps are allowed. Once connected, the app follows your ChatGPT account.
Connecting is free. A free Fast WebP Converter account is the way to try it: 50 conversions a month on the server, shared by Claude, ChatGPT, every MCP client and the API. Pro is full access, paid monthly, yearly or once for life ($4.99/month, $29/year or $59 once), with 10,000 server conversions a month (fair use). The monthly allowance resets on the 1st (UTC).
The app is an MCP server: each person signs in with their own account, every tool is available (conversion, batches, page audits, account) and results show as a card. A Custom GPT calls the REST API through an action with one API key, so it suits a private or team GPT.
The app converts images by URL. For files on your computer, the browser converter on https://www.fastwebpconverter.com converts whole folders without uploading anything, and the API accepts uploads up to 4 MB.
Related
WebP from the chat
Create your free account (50 conversions a month), add the app with https://www.fastwebpconverter.com/api/mcp, and ask ChatGPT for your first conversion.