What is tiktoken-rs?

toeverything/tiktoken-rs — explained in plain English

Analysis updated 2026-07-07 · repo last pushed 2024-05-14

★ 1RustAudience · developerComplexity · 2/5DormantSetup · easy

Mindmap

mindmap
  root((repo))
    What it does
      Counts tokens accurately
      Matches OpenAI rules
      Checks remaining space
    Use cases
      Chat app limits
      Cost estimation
      Pre-check long docs
    Tech stack
      Rust
      OpenAI encodings
    Audience
      Rust developers
      AI app builders

mindmap root((repo)) What it does Counts tokens accurately Matches OpenAI rules Checks remaining space Use cases Chat app limits Cost estimation Pre-check long docs Tech stack Rust OpenAI encodings Audience Rust developers AI app builders

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What do people build with it?

USE CASE 1

Check if user-pasted text exceeds a model's token limit before sending it to OpenAI.

USE CASE 2

Estimate API costs by counting tokens in outgoing requests ahead of time.

USE CASE 3

Calculate how many tokens are left for an AI response in a chat conversation.

What is it built with?

RustOpenAI

How does it compare?

	toeverything/tiktoken-rs	abyo-software/ferro-stash	ariasbruno/glyph
Stars	1	1	1
Language	Rust	Rust	Rust
Last pushed	2024-05-14	—	—
Maintenance	Dormant	—	—
Setup difficulty	easy	moderate	easy
Complexity	2/5	4/5	2/5
Audience	developer	ops devops	developer

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · easy Time to first run · 5min

Rust library that can be added to a project with a standard dependency entry, no external services or API keys needed just to count tokens locally.

No license information was provided in the explanation, so the usage terms are unknown.

So what is it?

When you send text to an AI model like GPT-4, it doesn't actually read words. It reads "tokens," which are chunks of text that might be a whole word or just part of one. Knowing exactly how many tokens your text contains matters a lot because OpenAI charges by the token, and every model has a strict limit on how many tokens it can process at once. This project, called tiktoken-rs, lets developers build apps in the Rust programming language that can count those tokens accurately before sending anything to OpenAI. The library works by replicating the exact rules OpenAI uses to chop text into tokens. A developer gives it a string of text, and it returns the token count using the correct method for whichever model they're targeting, whether that's GPT-4o, GPT-3, or an older editing model. It can also figure out how much room is left in a conversation, so a developer can calculate the maximum number of tokens the AI's response can be without hitting an error. Someone building a chat app powered by GPT-4 would find this useful. If a user pastes in a very long document, the app needs to know whether that text exceeds the model's limit before attempting to send it. It also helps developers estimate costs, since they can see the token count of outgoing requests ahead of time. The project supports all of OpenAI's current and recent encoding schemes, so it covers the full range of their models. The notable thing here is that it's written in Rust, a language known for speed and reliability, rather than in Python where most AI tooling lives. Developers already working in Rust get a native tool that fits their existing workflow without needing to bridge over to another language just to count tokens.

Copy-paste prompts

Prompt 1

Using tiktoken-rs, write a Rust function that takes a string and a model name, and returns the token count so I can check if it fits within the model's context limit.

Prompt 2

Build a Rust helper with tiktoken-rs that calculates how many tokens are remaining in a GPT-4o conversation, so I can set the max response length without hitting errors.

Prompt 3

Use tiktoken-rs in my Rust project to count tokens of a long document and estimate the OpenAI API cost before making the request.

Frequently asked questions