1
ChatGPT
OpenAI · Free · Plus $20/mo · Pro tier above it
1.05M tokens on GPT-6 Astra, with 128K output, documented in OpenAI's own model docs — the largest published figure in this comparison.
Filtered comparison
ChatGPT alternatives with the largest context windows.
By Daniel Reeve · figures read at source 2026-09-10 · page updated 2026-09-18
Context window is the number people plan around when the work involves long documents, large codebases or a lot of pasted material. It is also the number vendors are least consistent about publishing. We list only figures we could read at the vendor's own source, and we name the ones we could not.
Qualifies3 of 10 tools
Figures read at source2026-09-10
Unverified figuresPublished as gaps, not guessed
The shortlist
3 that qualify.
Context window is the number people plan around when the work involves long documents, large codebases or a lot of pasted material. It is also the number vendors are least consistent about publishing. We list only figures we could read at the vendor's own source, and we name the ones we could not.
| Tool | Best for | Price | Free tier | Context window | Web search | File upload | Image gen | Cited sources | EU hosting | Open weights | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| ChatGPT | General-purpose work, the widest tool ecosystem | Free · Plus $20/mo · Pro tier above it | Yes — with lower limits | 1.05M tokens (GPT-6 Astra) | Yes | Yes | Yes | Partial | No | No | Open ↗ |
 Claude |
Writing, analysis, long documents | Free · Pro $20/mo ($17 annually) · Max from $100 | Yes — Sonnet and Haiku, 5-hour rolling window | 1M tokens · 128K output | No | Yes | No | No | No | No | Open ↗ |
 Grok |
High-volume generation, current topics | API $2.00 in / $6.00 out per 1M tokens | Limited | 500K tokens · cutoff 1 Feb 2026 | Yes | Partial | Yes | Partial | No | Not verified | Open ↗ |
Read from each vendor's own pages on 2026-09-10. Cells marked Not verified are gaps we could not close at source — we publish them rather than copy a figure from another comparison. How we test.
One by one
What each one is actually like.
2
Claude
Anthropic · Free · Pro $20/mo ($17 annually) · Max from $100
1M tokens with 128K output, documented. Combined with the best long-document handling here, this is the most useful large window of the set for writing and analysis work.
3
Grok
xAI · API $2.00 in / $6.00 out per 1M tokens
500K tokens, documented, with a training cutoff of 1 February 2026 — so the window is large but the knowledge behind it is not current unless search is switched on.
The honest part
The vendors who do not publish a figure.
Google, Mistral, DeepSeek, Perplexity and Meta do not publish per-model context windows in a form we could verify at source. That is not an accusation of anything — it means we will not print a number for them, because a figure repeated from another comparison article is not a source. If you need to plan capacity around a context limit, treat an unpublished window as a risk rather than a detail.
Questions
Frequently asked.
Which ChatGPT alternative has the largest context window?
Claude, at a documented 1M tokens with 128K output — marginally behind ChatGPT's own GPT-6 Astra at 1.05M. Grok publishes 500K. No other vendor in this comparison publishes a per-model figure we could verify.
Why do you not list a context window for Gemini or DeepSeek?
Because neither publishes one per model where we could read it at source. We would rather print a gap than a number copied from another article. If you find a documented figure on the vendor's own pages, it supersedes this page — tell us and we will update it.
Does a bigger context window actually help?
For long documents and large codebases, yes, materially. For everyday questions it changes nothing, and a large window does not by itself mean the model uses the far end of it well. Test on your own longest realistic input before paying for headroom.