GLM 5.3 Flash API

About GLM 5.3 Flash

Natively multimodal flash model with a 1M token context, image and video input, always-on reasoning, native web search, and tool calling.

Notes: - Context window: 1M tokens - Maximum output: 128K tokens - Accepts text, image, video, and file input - Always reasons; thinking cannot be disabled - Reasoning effort: low, high, or max (max recommended for complex coding) - A request for a different effort, or to turn thinking off, is served at the nearest supported level - Built-in web search adds $0.033 per request when used - Supports function calling, structured output (JSON mode), and streaming

Also known as GLM Flash, Z.ai GLM 5.3 Flash

GLM 5.3 Flash specs

Model ID

glm-5-3-flash

Provider

Z.ai

Category

Text Generation

Released

Aug 26, 2026

Context window

1M tokens

Max output

131,072 tokens

Input

TextImageVideoFile

Output

Text

Structured output

JSON Mode

Region

Singapore

Endpoints

POST/v1/chat/completionsPOST/v1/responsesPOST/v1/messagesPOST/v1beta/models/glm-5-3-flash:generateContent

Alternate model IDs

glm-5.3-flashzai/glm-5.3-flashzhipu/glm-5.3-flash

GLM 5.3 Flash API pricing

Live pay-as-you-go rates from the EmpirioLabs catalog. You are billed only for what you use, with no monthly minimum.

How to call the GLM 5.3 Flash API

GLM 5.3 Flash serves the OpenAI-compatible Chat Completions API. Point any OpenAI SDK at https://api.empiriolabs.ai/v1 with your EmpirioLabs API key and use the model id glm-5-3-flash. Get an API key from the EmpirioLabs dashboard.

curl https://api.empiriolabs.ai/v1/chat/completions \
  -H "Authorization: Bearer $EMPIRIOLABS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "glm-5-3-flash",
    "messages": [
      {"role": "user", "content": "Write a haiku about the ocean."}
    ]
  }'

from openai import OpenAI

client = OpenAI(
    base_url="https://api.empiriolabs.ai/v1",
    api_key="YOUR_EMPIRIOLABS_API_KEY",
)

response = client.chat.completions.create(
    model="glm-5-3-flash",
    messages=[{"role": "user", "content": "Write a haiku about the ocean."}],
)
print(response.choices[0].message.content)

GLM 5.3 Flash API parameters

Request parameters supported by the GLM 5.3 Flash API on EmpirioLabs. Defaults apply when a field is omitted.

GLM 5.3 Flash API: common questions

How much does the GLM 5.3 Flash API cost?

On EmpirioLabs, GLM 5.3 Flash is billed pay as you go: Input $0.075 per 1M prompt tokens; Output $0.25 per 1M generated tokens; Web search $0.033 per request. The live rate card on this page always matches what the API charges.

What is the context window of GLM 5.3 Flash?

GLM 5.3 Flash supports a 1M-token context window with up to 131,072 output tokens per response.

Is the GLM 5.3 Flash API OpenAI-compatible?

Yes. GLM 5.3 Flash serves the OpenAI-compatible Chat Completions API, so existing OpenAI SDKs work by pointing base_url at https://api.empiriolabs.ai/v1 and setting the model id to glm-5-3-flash.

Can I try GLM 5.3 Flash in the browser before integrating?

Yes. The EmpirioLabs playground runs GLM 5.3 Flash in the browser with the same parameters the API exposes, so you can test prompts before writing code.

How do I get a GLM 5.3 Flash API key?

Create an EmpirioLabs account, then generate a key under API Keys in the dashboard. Billing is pay-as-you-go credits, so you only pay for the requests you make.