GPT-5.5 Instant vs Mercury 2
GPT-5.5 Instant leads the LLM Stats Score 32.3 to 23.6. Mercury 2 is 30.0x cheaper per token.
OpenAI · Inception · Updated for 2026
Which is better?
GPT-5.5 Instant leads the overall LLM Stats Score 32.3 to 23.6, ranking #106 overall.
The models split the 2 individual benchmarks reported for both models evenly.
On price, Mercury 2 is roughly 30.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.5 Instant also accepts a larger context window (400,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose GPT-5.5 Instant
- overall performance matters — it scores 32.3 and ranks #106 on LLM Stats
- your work emphasizes reasoning — it leads those capability indexes
- you process long inputs — it offers a 400,000 token context window
- you want the most recent training data — it shipped May 2026
Choose Mercury 2
- cost matters — it's about 30.0x cheaper per token
At a glance
The differences that matter most.
Individual benchmarks
9 reported for GPT-5.5 Instant · 6 for Mercury 2
GPT-5.5 Instant outperforms in 1 benchmarks (GPQA), while Mercury 2 is better at 1 benchmark (AIME 2025).
Both models are evenly matched across the benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-5.5 Instant ($5.00/1M tokens) is 20.0x more expensive than Mercury 2 ($0.25/1M tokens).
For output processing, GPT-5.5 Instant ($30.00/1M tokens) is 40.0x more expensive than Mercury 2 ($0.75/1M tokens).
In conclusion, GPT-5.5 Instant is more expensive than Mercury 2.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.5 Instant accepts 400,000 input tokens compared to Mercury 2's 128,000 tokens. GPT-5.5 Instant can generate longer responses up to 128,000 tokens, while Mercury 2 is limited to 8,192 tokens.
Input capabilities
Documented input modalities across available providers
GPT-5.5 Instant supports multimodal inputs, whereas Mercury 2 does not.
GPT-5.5 Instant can handle both text and other forms of data like images, making it suitable for multimodal applications.
GPT-5.5 Instant
Mercury 2
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
GPT-5.5 Instant was released on 2026-05-05, while Mercury 2 was released on 2026-02-24.
GPT-5.5 Instant is 2 months newer than Mercury 2.
May 5, 2026
4 months ago
2mo newerFeb 24, 2026
6 months ago
Knowledge Cutoff
When training data ends
GPT-5.5 Instant has a documented knowledge cutoff of 2025-08-31, while Mercury 2's cutoff date is not specified.
We can confirm GPT-5.5 Instant's training data extends to 2025-08-31, but cannot make a direct comparison without Mercury 2's cutoff date.
Aug 2025
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Provider Availability
GPT-5.5 Instant is available from OpenAI. Mercury 2 is available from Inception.
GPT-5.5 Instant
Mercury 2
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-5.5 Instant and Mercury 2 side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-5.5 Instant vs Mercury 2.