What is the difference between Claude Opus 5.5 and Gemini 2.5 Flash Preview 05-20?

Claude Opus 5.5 is developed by Anthropic while Gemini 2.5 Flash Preview 05-20 is developed by Google AI. Claude Opus 5.5 has a 1.0M token context window vs Gemini 2.5 Flash Preview 05-20's 1.0M. You can compare their actual outputs across 1 challenges on Rival to see how they differ in practice.

Which is better, Claude Opus 5.5 or Gemini 2.5 Flash Preview 05-20?

It depends on your use case. Claude Opus 5.5 and Gemini 2.5 Flash Preview 05-20 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 1 challenges so you can judge which fits your needs best.

How much does Claude Opus 5.5 cost compared to Gemini 2.5 Flash Preview 05-20?

Claude Opus 5.5 costs $4/M input tokens and Gemini 2.5 Flash Preview 05-20 costs $0.15/M input tokens. Gemini 2.5 Flash Preview 05-20 is $3.85/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

How can I compare Claude Opus 5.5 and Gemini 2.5 Flash Preview 05-20 on Rival?

This page shows a side-by-side comparison of Claude Opus 5.5 and Gemini 2.5 Flash Preview 05-20 across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

Updated Sep 2026

Claude Opus 5.5vsGemini 2.5 Flash Preview 05-20

Gemini 2.5 Flash Preview 05-20 is cheaper than Claude Opus 5.5 at $0.15/M vs $4/M input tokens.

Claude Opus 5.5 and Gemini 2.5 Flash Preview 05-20 compared across 1 shared prompts
Spec	Claude Opus 5.5	Gemini 2.5 Flash Preview 05-20
Input price	$4/M tokens	$0.15/M tokens
Output price	$20/M tokens	$0.6/M tokens
Context window	1.0M tokens	1.0M tokens
Weights	Closed	—
Free API (OpenRouter)	No	No
Released	Sep 2026	May 2025

Our Verdict

Claude Opus 5.5

Gemini 2.5 Flash Preview 05-20Runner-up

Not enough votes to call it. On the specs, Claude Opus 5.5 has the edge: bigger model tier, newer.

Gemini 2.5 Flash Preview 05-20 costs 33x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Opus 5.5

Input

$4.00

Output

$20.00

Gemini 2.5 Flash Preview 05-20

Input

$0.15

27× cheaper

Output

$0.60

33× cheaper

Gemini 2.5 Flash Preview 05-20 is cheaper on both: 27× input, 33× output.

Where to run it

4 hosts

Claude Opus 5.54 hosts

HostInOutContextUptime

Amazon Bedrock$4.00 in$20.00 out1M99.8% up Azure AI Foundry$4.00 in$20.00 out1M100% up Anthropic$4.00 in$20.00 out1M100% up Google Vertex AI$4.00 in$20.00 out1M100% up

Gemini 2.5 Flash Preview 05-20

No hosts listed on OpenRouter.

Per million tokens. Prices and uptime via OpenRouter, checked 25 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

Keep exploring

More comparisons

Cost per 1M tokens

4 hosts

What we learned reading every model

Common questions

What is the difference between Claude Opus 5.5 and Gemini 2.5 Flash Preview 05-20?

Which is better, Claude Opus 5.5 or Gemini 2.5 Flash Preview 05-20?

How much does Claude Opus 5.5 cost compared to Gemini 2.5 Flash Preview 05-20?

How can I compare Claude Opus 5.5 and Gemini 2.5 Flash Preview 05-20 on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages

Cost per 1M tokens

4 hosts

What we learned reading every model

Common questions

What is the difference between Claude Opus 5.5 and Gemini 2.5 Flash Preview 05-20?

Which is better, Claude Opus 5.5 or Gemini 2.5 Flash Preview 05-20?

How much does Claude Opus 5.5 cost compared to Gemini 2.5 Flash Preview 05-20?

How can I compare Claude Opus 5.5 and Gemini 2.5 Flash Preview 05-20 on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages