GPT-5.1: Everything You Need to Know (2026)
Features, pricing, capabilities, and how to get started
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GPT-5.1: Everything You Need to Know in 2026
OpenAI's GPT-5.1 represents the latest iteration in the GPT model family, building on the foundation of GPT-5 with refined capabilities across reasoning, code generation, multimodal understanding, and instruction following. Whether you are evaluating it for personal use, team deployment, or API integration, this guide covers everything you need to know.
What Is GPT-5.1?
GPT-5.1 is an updated version of OpenAI's GPT-5 model, positioned as a refinement rather than a generational leap. Think of it as GPT-5 with improved reliability, better tool use, enhanced reasoning in edge cases, and expanded context handling.
| Specification | GPT-5.1 |
|---|---|
| Developer | OpenAI |
| Architecture | Transformer (details proprietary) |
| Context Window | 256K tokens |
| Max Output | 32K tokens |
| Training Data Cutoff | Late 2025 |
| Multimodal | Text, images, audio, video input |
| Tool Use | Native function calling, code interpreter |
| Available Via | ChatGPT, API, Azure OpenAI |
Key Improvements Over GPT-5
GPT-5.1 is not a complete new model, but it includes meaningful upgrades:
1. Improved Instruction Following
GPT-5.1 is significantly better at following complex, multi-step instructions without drifting or skipping requirements. In internal evaluations, it shows a measurable reduction in "instruction amnesia" on long prompts.
2. Enhanced Reasoning Consistency
While GPT-5 occasionally produced inconsistent reasoning chains, 5.1 demonstrates more stable chain-of-thought outputs, particularly in mathematical proofs and logical deductions.
3. Better Code Generation
| Benchmark | GPT-5 | GPT-5.1 | Improvement |
|---|---|---|---|
| HumanEval | 90.2% | 93.1% | +2.9% |
| MBPP+ | 85.7% | 89.3% | +3.6% |
| SWE-bench Verified | 52.1% | 57.8% | +5.7% |
| LiveCodeBench | 71.3% | 76.2% | +4.9% |
4. Expanded Multimodal Capabilities
GPT-5.1 handles complex visual reasoning better, including multi-image comparisons, dense document parsing, and video frame analysis with improved temporal understanding.
5. Function Calling Reliability
For developers using GPT-5.1 through the API, function calling (tool use) is more reliable with fewer hallucinated parameters and better schema adherence.
How to Access GPT-5.1
ChatGPT (Web and Mobile)
- Go to chat.openai.com
- If you are a Plus, Team, or Enterprise subscriber, select GPT-5.1 from the model picker
- Free tier users may have limited access to GPT-5.1 (check current availability)
OpenAI API
curl https://api.openai.com/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $OPENAI_API_KEY" \
-d '{
"model": "gpt-5.1",
"messages": [
{"role": "system", "content": "You are a helpful assistant."},
{"role": "user", "content": "Explain the CAP theorem with a practical example."}
],
"temperature": 0.7,
"max_tokens": 2048
}'
Using the Python SDK:
from openai import OpenAI
client = OpenAI()
response = client.chat.completions.create(
model="gpt-5.1",
messages=[
{"role": "system", "content": "You are a helpful coding assistant."},
{"role": "user", "content": "Write a Python function that implements binary search with detailed comments."}
],
temperature=0,
max_tokens=2048
)
print(response.choices[0].message.content)
Using the Node.js SDK:
import OpenAI from 'openai';
const openai = new OpenAI();
const completion = await openai.chat.completions.create({
model: 'gpt-5.1',
messages: [
{ role: 'system', content: 'You are a helpful assistant.' },
{ role: 'user', content: 'Design a REST API for a task management app.' }
],
temperature: 0.7,
});
console.log(completion.choices[0].message.content);
Azure OpenAI
For enterprise users on Azure:
curl "https://YOUR_RESOURCE.openai.azure.com/openai/deployments/gpt-51/chat/completions?api-version=2025-12-01" \
-H "Content-Type: application/json" \
-H "api-key: $AZURE_OPENAI_API_KEY" \
-d '{
"messages": [
{"role": "user", "content": "Summarize the key changes in GDPR 2025 amendments."}
]
}'
GPT-5.1 Pricing
| Tier | Input Tokens | Output Tokens | Notes |
|---|---|---|---|
| Standard | $2.50 / 1M tokens | $10.00 / 1M tokens | Default tier |
| Batch API | $1.25 / 1M tokens | $5.00 / 1M tokens | 50% discount, async |
| Cached Input | $1.25 / 1M tokens | $10.00 / 1M tokens | For repeated prompts |
Cost comparison with other models:
| Model | Input (per 1M) | Output (per 1M) |
|---|---|---|
| GPT-5.1 | $2.50 | $10.00 |
| GPT-4o | $2.50 | $10.00 |
| Claude Opus 4 | $15.00 | $75.00 |
| Claude Sonnet 4 | $3.00 | $15.00 |
| Gemini 2.5 Pro | $1.25 | $10.00 |
When to Use GPT-5.1 vs. Other Models
| Use Case | Best Model | Why |
|---|---|---|
| Complex coding tasks | GPT-5.1 or Claude Sonnet 4 | Strong code gen with good instruction following |
| Creative writing | Claude Opus 4 or GPT-5.1 | Both excel at nuanced, long-form writing |
| Data analysis | GPT-5.1 (with Code Interpreter) | Built-in execution environment |
| Quick factual answers | GPT-4o-mini or Gemini Flash | Cheaper and faster for simple queries |
| Math and reasoning | o3 or QwQ | Purpose-built reasoning models |
| Image understanding | GPT-5.1 or Gemini 2.5 Pro | Both have strong vision capabilities |
| Cost-sensitive apps | GPT-4o-mini or Claude Haiku | 10-20x cheaper per token |
| Enterprise compliance | GPT-5.1 via Azure | Azure's enterprise security features |
Advanced Features
Function Calling (Tool Use)
GPT-5.1 has improved function calling with better parameter extraction:
from openai import OpenAI
client = OpenAI()
tools = [
{
"type": "function",
"function": {
"name": "get_weather",
"description": "Get current weather for a location",
"parameters": {
"type": "object",
"properties": {
"location": {
"type": "string",
"description": "City and state, e.g. San Francisco, CA"
},
"unit": {
"type": "string",
"enum": ["celsius", "fahrenheit"]
}
},
"required": ["location"]
}
}
}
]
response = client.chat.completions.create(
model="gpt-5.1",
messages=[{"role": "user", "content": "What's the weather in Tokyo?"}],
tools=tools,
tool_choice="auto"
)
print(response.choices[0].message.tool_calls)
Structured Outputs
Force GPT-5.1 to return valid JSON matching a specific schema:
response = client.chat.completions.create(
model="gpt-5.1",
messages=[
{"role": "user", "content": "List 3 programming languages with their key features"}
],
response_format={
"type": "json_schema",
"json_schema": {
"name": "languages",
"schema": {
"type": "object",
"properties": {
"languages": {
"type": "array",
"items": {
"type": "object",
"properties": {
"name": {"type": "string"},
"paradigm": {"type": "string"},
"key_feature": {"type": "string"}
},
"required": ["name", "paradigm", "key_feature"]
}
}
},
"required": ["languages"]
}
}
}
)
Vision (Image Input)
response = client.chat.completions.create(
model="gpt-5.1",
messages=[
{
"role": "user",
"content": [
{"type": "text", "text": "What's in this image? Describe it in detail."},
{
"type": "image_url",
"image_url": {
"url": "https://example.com/photo.jpg"
}
}
]
}
]
)
Tips for Getting the Best Results
Use system messages effectively. GPT-5.1 is very responsive to well-crafted system prompts. Define the role, tone, constraints, and output format clearly.
Set temperature based on task. Use 0 for factual/coding tasks, 0.7-1.0 for creative tasks.
Use structured outputs when you need reliable JSON. Do not just ask for JSON in the prompt; use the
response_formatparameter.Leverage the 256K context window for long document analysis, but be mindful of cost. Input tokens add up fast with large contexts.
Use the Batch API for non-time-sensitive workloads. You get 50% off and results within 24 hours.
Compare with o3 for pure reasoning tasks. GPT-5.1 is a generalist; o3 is a reasoning specialist.
Wrapping Up
GPT-5.1 is a solid evolution of GPT-5, delivering meaningful improvements in reliability, code generation, and multimodal understanding without a dramatic price increase. For most developers, it is a strong default choice for general-purpose LLM tasks.
The AI landscape is broader than just language models, though. If your application also needs image generation, video creation, lip sync, voice cloning, or other media capabilities, Hypereal AI provides a unified API that lets you access GPT-5.1 alongside dozens of specialized AI models, all through a single integration.
