GPT-5.1 Instant vs Seed 1.8
GPT-5.1 Instant and Seed 1.8 are closely matched at 36.6 and 34.2 on the LLM Stats Score. Seed 1.8 is 5.0x cheaper per token.
OpenAI · ByteDance · Updated for 2026
Which is better?
GPT-5.1 Instant and Seed 1.8 are closely matched on the overall LLM Stats Score at 36.6 and 34.2.
In the 3 individual benchmarks reported for both models, GPT-5.1 Instant wins 2; this is a narrower head-to-head signal than the composite indexes.
On price, Seed 1.8 is roughly 5.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.1 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-5.1 Instant
- you value its reported benchmark strengths — it wins 2 of 3 exact shared results
- you process long inputs — it offers a 400,000 token context window
Choose Seed 1.8
- cost matters — it's about 5.0x cheaper per token
- you want the most recent training data — it shipped Feb 2026
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
9 reported for GPT-5.1 Instant · 57 for Seed 1.8
GPT-5.1 Instant outperforms in 2 benchmarks (MMMU, SWE-Bench Verified), while Seed 1.8 is better at 1 benchmark (AIME 2025).
GPT-5.1 Instant shows notably better performance in the majority of benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-5.1 Instant ($1.25/1M tokens) is 5.0x more expensive than Seed 1.8 ($0.25/1M tokens).
For output processing, GPT-5.1 Instant ($10.00/1M tokens) is 5.0x more expensive than Seed 1.8 ($2.00/1M tokens).
In conclusion, GPT-5.1 Instant is more expensive than Seed 1.8.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.1 Instant accepts 400,000 input tokens compared to Seed 1.8's 256,000 tokens. Seed 1.8 can generate longer responses up to 256,000 tokens, while GPT-5.1 Instant is limited to 128,000 tokens.
Input capabilities
Documented input modalities across available providers
Both GPT-5.1 Instant and Seed 1.8 support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
GPT-5.1 Instant
Seed 1.8
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-5.1 Instant was released on 2025-11-12, while Seed 1.8 was released on 2026-02-17.
Seed 1.8 is 3 months newer than GPT-5.1 Instant.
Nov 12, 2025
10 months ago
Feb 17, 2026
6 months ago
3mo newerKnowledge Cutoff
When training data ends
Neither model specifies a knowledge cutoff date.
Unable to compare the recency of their training data.
Provider Availability
GPT-5.1 Instant is available from OpenAI. Seed 1.8 is available from DeepInfra.
GPT-5.1 Instant
Seed 1.8
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-5.1 Instant and Seed 1.8 side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-5.1 Instant vs Seed 1.8.