GLM 5.3 Flash API: Z.ai's chat / LLM model, one key away
GLM 5.3 Flash via the ApexApi gateway
GLM 5.3 Flash is the low cost, natively multimodal member of Z.AI's GLM-5.3 family: it reads images as well as text and has a 1M token context window. Choose it for high volume chat, vision and tool calling where GLM 5.3 would be overkill. Call it through ApexApi's unified, OpenAI-compatible API with one `ak-` key, alongside every other model in the catalog. It supports a 1,000,000-token context window, tool / function calling, image (vision) input, and streaming responses. Pricing is $0.18 input and $0.60 output per 1M tokens, billed pay-per-use from your credit balance with no subscription.
GLM 5.3 Flash is served through ApexApi's unified, OpenAI-compatible API. One key, one format, with smart routing and automatic failover. Provider: Z.ai.
Why GLM 5.3 Flash
1,000,000-token context
Reason over long documents, codebases, and multi-turn history in a single request.
Tool & function calling
Structured outputs and tool orchestration for agentic and automation workloads.
Vision input
Send images alongside text for document, UI, and visual-understanding tasks.
Specifications
- Modality
- chat
- Context window
- 1000K tokens
- Max output
- 24.6K tokens
- Streaming
- Yes
- Tool / function calling
- Yes
- Vision input
- Yes
GLM 5.3 Flash pricing
- A million tokens in and a million out costs $0.78 here, all-in.
- That makes it the 13th cheapest of the 81 chat models we serve, ranked on output price.
- It runs 8.8× cheaper than GLM 5.3, the pricier option from the same maker.
Getting started with GLM 5.3 Flash
OpenAI-compatible. Point your client at ApexApi, swap your key, and call it. No new SDK to learn.
from openai import OpenAI
client = OpenAI(
base_url="https://api.apexapi.dev/v1",
api_key="<YOUR_APEXAPI_KEY>",
)
response = client.chat.completions.create(
model="zai/glm-5.3-flash",
messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)GLM 5.3 Flash use cases
What teams build with GLM 5.3 Flash on ApexApi.
Agents & automation
Tool-using agents that orchestrate multi-step workflows and call APIs.
Coding assistants
Code generation, refactoring, reviews, and multi-file reasoning.
RAG & knowledge apps
Summarization and long-document Q&A grounded in your own data.
GLM 5.3 Flash vs other models
How it compares, and on ApexApi you can switch between any of them with a single string change, same key, same endpoint.
GLM 5.3 Flash vs Claude Opus 4.7
Compare GLM 5.3 Flash against this model on price, capabilities, and latency. A/B them with a single key on ApexApi.
Learn more about Claude Opus 4.7 API →GLM 5.3 Flash vs GPT-5.5
Compare GLM 5.3 Flash against this model on price, capabilities, and latency. A/B them with a single key on ApexApi.
Learn more about GPT-5.5 API →GLM 5.3 Flash vs Gemini 3.1 Pro Preview
Compare GLM 5.3 Flash against this model on price, capabilities, and latency. A/B them with a single key on ApexApi.
Learn more about Gemini 3.1 Pro Preview API →GLM 5.3 Flash API: FAQ
How do I call GLM 5.3 Flash through ApexApi?
Create an ApexApi key, point your client at https://api.apexapi.dev/v1, and POST to /v1/chat/completions with the model set to `zai/glm-5.3-flash`. The API is OpenAI-compatible, so an existing OpenAI SDK works once you change the base URL and key.
How much does GLM 5.3 Flash cost on ApexApi?
$0.18 per million input tokens and $0.60 per million output tokens, all-in with no separate platform fee. You buy credits and pay per call, with no subscription or minimum.
What is the context window for GLM 5.3 Flash?
1,000,000 tokens. It can return up to 24,576 tokens in a single response.
Does GLM 5.3 Flash support tool calling and image input?
GLM 5.3 Flash supports tool / function calling, image (vision) input, and streaming responses.
What should I use instead of GLM 5.3 Flash?
From the same maker, GLM 5.3 FlashX is the step up when this one falls short. Switching is one string: it runs on the same endpoint and the same key, so there is nothing to re-integrate.
Ready to build with GLM 5.3 Flash?
One API key. Every major AI model. Pay only for what you use.
Try GLM 5.3 Flash, pay as you go from $5