Context window fit check

Client

Paste a draft and pick a context window size to see rough usage, remaining budget, and overflow. Complements context split & budget.

Draft text

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Token counts use the same CJK-aware chars/token heuristic as the token estimate page. Reserve headroom for tools, images, and tokenizer drift.

~40 / 128,000 tokens0.0%
Characters
157
Rough tokens
40
Remaining
127,960
Status
Fits

Nearby workflows on Toolcore

  • LLM token estimateRough character-based token planning for prompts and context—CJK-aware heuristic, browser-only—not tokenizer-exact. when you want a second pass with AI-assisted explanation on Toolcore.
  • LLM context split & budgetSplit pasted prompt blocks by a delimiter and see per-section rough token share and optional budget compare—browser-only, not tokenizer-exact. when you want a second pass with AI-assisted explanation on Toolcore.
  • Long text chunker for chat pasteSplit long pasted prose into sequential under-the-limit blocks—paragraph, line, or fixed character breaks—browser-only; not tokenizer-exact. when you want a second pass with AI-assisted explanation on Toolcore.
  • LLM character budget from token capPlan max paste characters from a target token budget—same CJK-aware heuristic as token estimate, browser-only, not tokenizer-exact. when you want a second pass with AI-assisted explanation on Toolcore.

Common use cases

  • Check if a RAG bundle plus system prompt still fits a 128K window before sending.
  • Switch between 8K, 32K, and 200K presets when comparing model tiers.
  • Spot overflow early and trim with long text chunker or whitespace savings.

Common mistakes to avoid

  • Ignoring tool definitions and image tokens

    This counts pasted text only—reserve extra budget for tools, JSON schema, and vision payloads.

  • Assuming 100% fill is safe

    Leave headroom for the model reply and tokenizer drift; aim below ~85% for drafts.

FAQ

Is this the official tokenizer?

No. It uses the same CJK-aware character heuristic as our token estimate page.

Does text leave my browser?

No. Statistics are computed locally.

Related utilities you can open in another tab—mostly client-side.