What is the difference between Claude 3 Opus and Claude Fable 5.1?

Both are developed by Anthropic but target different use cases. Claude 3 Opus has a 200K token context window vs Claude Fable 5.1's 1.0M. You can compare their actual outputs across 2 challenges on Rival to see how they differ in practice.

Which is better, Claude 3 Opus or Claude Fable 5.1?

It depends on your use case. Claude 3 Opus and Claude Fable 5.1 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 2 challenges so you can judge which fits your needs best.

How much does Claude 3 Opus cost compared to Claude Fable 5.1?

Claude 3 Opus costs $15/M input tokens and Claude Fable 5.1 costs $10/M input tokens. Claude Fable 5.1 is $5.00/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 3 Opus and Claude Fable 5.1 on Rival?

This page shows a side-by-side comparison of Claude 3 Opus and Claude Fable 5.1 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 3 OpusvsClaude Fable 5.1

Claude Fable 5.1 is cheaper than Claude 3 Opus at $10/M vs $15/M input tokens.

Claude 3 Opus and Claude Fable 5.1 compared across 2 shared prompts
Spec	Claude 3 Opus	Claude Fable 5.1
Input price	$15/M tokens	$10/M tokens
Output price	$75/M tokens	$50/M tokens
Context window	200K tokens	1.0M tokens
Weights	—	Closed
Free API (OpenRouter)	No	No
Released	Mar 2024	Sep 2026

Our Verdict

Claude Fable 5.1

Claude 3 OpusRunner-up

Not enough votes to call it. On the specs, Claude Fable 5.1 has the edge: newer, bigger context window.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude 3 Opus

Input

$15.00

Output

$75.00

Claude Fable 5.1

Input

$10.00

1.5× cheaper

Output

$50.00

1.5× cheaper

Claude Fable 5.1 is cheaper on both: 1.5× input, 1.5× output.

Where to run it

4 hosts

Claude 3 Opus

No hosts listed on OpenRouter.

Claude Fable 5.14 hosts

HostInOutContextUptime

Amazon Bedrock$10.00 in$50.00 out1M—Anthropic$10.00 in$50.00 out1M99.1% up Azure AI Foundry$10.00 in$50.00 out1M99.1% up Google Vertex AI$10.00 in$50.00 out1M99.8% up

Per million tokens. Prices and uptime via OpenRouter, checked 16 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

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More comparisons

Cost per 1M tokens

4 hosts

What we learned reading every model

Common questions

What is the difference between Claude 3 Opus and Claude Fable 5.1?

Which is better, Claude 3 Opus or Claude Fable 5.1?

How much does Claude 3 Opus cost compared to Claude Fable 5.1?

How can I compare Claude 3 Opus and Claude Fable 5.1 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 3 Opus and Claude Fable 5.1?

Which is better, Claude 3 Opus or Claude Fable 5.1?

How much does Claude 3 Opus cost compared to Claude Fable 5.1?

How can I compare Claude 3 Opus and Claude Fable 5.1 on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages