gpt-oss-20b

reasoningapache-2.020B

`gpt-oss-20b` is our medium-sized open-weight model for low latency, local, or specialized use-cases (21B parameters with 3.6B active parameters).

Intelligence
Reasoning
Speed
Context
131K
Max output
131K

Capabilities

Reasoning & Interaction
Reasoning
Tool Calling
Output Control
Structured Output
JSON Mode
Infrastructure
Streaming
Batch Processing

Details

Provider OpenAI
Creator openai
Familygpt-oss
Licenseapache-2.0
Statusactive
Typereasoning
Input modalitiestext
Output modalitiestext
Open weightYes
Parameters20B
Architecture—
Context window131K tokens
Max input—
Max output131K tokens
Reasoning tokensYes
Knowledge cutoff
Release date—
Sourceofficial

Tools

Function Callingfunction_calling
Call external functions and APIs
Code Interpretercode_interpreter
Execute code in a sandbox
MCPmcp
Connect to Model Context Protocol servers
Web Searchweb_search
Search the web for information

Endpoints

ResponsesPOST
Stateful multi-turn conversationshttps://api.openai.com/v1/responses
BatchPOST
Async batch processing at lower costhttps://api.openai.com/v1/batches

Family Comparison: gpt-oss

ModelContextMax out
gpt-oss-120b131K131K
gpt-oss-20b131K131K

API

GET/v1/models/openai/gpt-oss-20b

gpt-oss-20b

`gpt-oss-20b` is our medium-sized open-weight model for low latency, local, or specialized use-cases (21B parameters with 3.6B active parameters).

gpt-oss-20b
Changes · 10 entries
gpt-oss-20bupdateca7a400Nov 2, 2026, 03:02 AM
description\→`gpt-oss-20b` is our medium-sized open-weight model for l...
gpt-oss-20bupdate118451aSep 24, 2026, 07:08 AM
description\→`gpt-oss-20b` is our medium-sized open-weight model for l...
gpt-oss-20bupdatee8ec634Mar 24, 2026, 07:27 PM
knowledge_cutoff2024-05→2024-06
gpt-oss-20bupdatefa2bbbbMar 24, 2026, 05:22 AM
capabilitiesjson modeno→yes
gpt-oss-20bupdatef43e286Mar 24, 2026, 04:45 AM
capabilitiesfine tuningyes→nojson modeyes→novisionnobatchyes
gpt-oss-20bupdate1cd659eMar 24, 2026, 04:19 AM
knowledge_cutoff2024-06→2024-05
capabilitiesfine tuningyesjson modeyes
page_urlhttps://platform.openai.com/docs/models/gpt-oss-20b→https://developers.openai.com/api/docs/models/gpt-oss-20b
gpt-oss-20bupdateb301ebeMar 23, 2026, 11:47 PM
knowledge_cutoff2024-05→2024-06
gpt-oss-20bupdate2b100acMar 23, 2026, 05:30 AM
licenseapache-2.0
parameters20
page_urlhttps://platform.openai.com/docs/models/gpt-oss-20b
open_weightyes
gpt-oss-20bupdateb50649fMar 21, 2026, 11:58 PM
descriptiongpt-oss-20b is an open-weight 21B parameter model release...→\
capabilitiesstreamingyes
knowledge_cutoff2024-05
model_typereasoning
reasoning_tokensyes
reasoning4
taglineMedium-sized open-weight model for low latency
tools["function_calling","code_interpreter","mcp","web_search"]
endpoints["responses","batch"]
snapshots["gpt-oss-20b"]
gpt-oss-20bcreate7f5c66fMar 21, 2026, 05:16 AM