ChatGPT vs Gemini vs Claude: Who writes the best Czech in 2026?
We tested three main AI assistants on ten typical work tasks. The results may surprise you.
Every week we get the same question: “Which AI assistant is best for Czech?” We decided to test it thoroughly - not with one prompt, but across ten real work situations.
We tested ChatGPT 4o, Google Gemini 1.5 Pro and Claude 3.5 Sonnet in March 2026.
How we tested
Each tool was given the same brief, with no prior conversation. We assessed:
- Language accuracy - grammar, punctuation, naturalness
- Relevance of the answer - does it actually answer what was asked?
- Length and concision - does it pad unnecessarily?
- Knowledge of Czech context - law, conventions, companies
Test scenarios
1. Write a rejection email to a customer
Brief: “Write an email rejecting a customer - we want to keep them, but their request isn’t feasible.”
| Tool | Rating | Note |
|---|---|---|
| ChatGPT 4o | ★★★★☆ | Good, but a bit formal |
| Gemini 1.5 Pro | ★★★☆☆ | Translated-sounding style, less natural |
| Claude 3.5 | ★★★★★ | Most natural Czech, right tone |
2. Summarise a contract (5 pages of text)
Brief: We fed in a sample lease agreement and asked for a summary of the key points.
Result: All three tools handled the basic summary. Claude was the only one to flag an unusual automatic-renewal clause that could be disadvantageous to the tenant. ChatGPT was the fastest, Gemini had the longest output with the most repetition.
3. Write a LinkedIn post
Brief: “Announce that the company has hired a new sales director.”
ChatGPT won here - its LinkedIn style was the most natural and it judged the post length well. Claude was too structured (it used bullet points), and Gemini wrote text that sounded translated from English.
4. Explain GDPR to me simply
Brief for a non-technical reader.
All three tools gave a solid explanation. Claude was the only one to mention specific Czech situations (e-shops, consent to processing) and the difference between consent and legitimate interest. Gemini used too many anglicisms.
5. Translate technical documentation
We translated an excerpt of API documentation from English into Czech.
Winner: ChatGPT 4o - it preserved technical terminology and correctly translated even less common terms. Claude came second, Gemini translated too literally.
6. Write terms and conditions for an e-shop
Warning: No AI tool should be the sole source of legal text. This was only an indicative comparison.
Claude produced the best-structured text with the most precise reference to Czech legislation (Act No. 89/2012 Coll.). ChatGPT and Gemini sometimes referenced the general European framework without Czech specifics.
7. Generate 10 content ideas
Brief: “10 blog ideas for an IT company focused on small Czech businesses.”
Winner: Claude - the ideas were specific, with a clear target reader. ChatGPT generated more generic ideas, Gemini repeated similar concepts.
8. Analysing Excel data (description of a table)
We described the structure of a data table and asked for a trend analysis.
Winner: ChatGPT - the best work with numbers and the ability to suggest charts.
9. Transcribing and editing spoken speech
We fed in a meeting transcript (40 minutes, 3,000 words) and asked for action items.
All three tools handled it. Claude stood out by assigning action items to specific people mentioned in the text.
10. Write a proposal for a new client
A business proposal for a fictional company for cloud backups.
Winner: Claude - it understood the sales context best and highlighted the right benefits. ChatGPT was too technical, Gemini too generic.
Overall results
| Tool | Score (out of 10) | Strength |
|---|---|---|
| Claude 3.5 Sonnet | 7/10 | Natural Czech, legal context, business writing |
| ChatGPT 4o | 6/10 | Translations, technical documentation, LinkedIn |
| Gemini 1.5 Pro | 4/10 | Solid foundation, but less natural Czech |
Recommendation
For writing and communication: Claude and ChatGPT are roughly equally good, with Claude slightly ahead on natural-sounding Czech.
For technical work and translations: ChatGPT 4o.
For everyday use in Czech: Try Claude - its output needs the least editing.
Prices (March 2026):
- ChatGPT Plus: 20 USD/month
- Claude Pro: 20 USD/month
- Gemini Advanced: 19 EUR/month (as part of Google One)
Gemini is the most accessible option for Google Workspace users - it’s built right into Gmail and Docs. That can be a decisive factor regardless of the test results.
Do you want to introduce AI in your company?
Flylight.ai helps Czech companies with AI implementation and automation: without needing an IT department.
Find out more →