Claude Token Counter. Anthropic released a token counting API for Claude a few days ago.
I built this tool for running prompts, images and PDFs against that API to count the tokens in them.
The API is free (albeit rate limited), but you'll still need to provide your own API key in order to use it.
Here's the source code. I built this using two sessions with Claude - one to build the initial tool and a second to add PDF and image support. That second one is a bit of a mess - it turns out if you drop an HTML file onto a Claude conversation it converts it to Markdown for you, but I wanted it to modify the original HTML source.
The API endpoint also allows you to specify a model, but as far as I can tell from running some experiments the token count was the same for Haiku, Opus and Sonnet 3.5.
Recent articles
- V&A East Storehouse and Operation Mincemeat in London - 27th August 2025
- The Summer of Johann: prompt injections as far as the eye can see - 15th August 2025
- Open weight LLMs exhibit inconsistent performance across providers - 15th August 2025