GLM 5.3 FlashX API: Z.ai's chat / LLM model, one key away
GLM 5.3 FlashX via the ApexApi gateway
GLM 5.3 FlashX is the speed tier of Z.AI's GLM-5.3 family, priced between GLM 5.3 and GLM 5.3 Flash, with a 1M token context window. Choose it for latency sensitive agents that need more than Flash but not the flagship. 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, and streaming responses. Pricing is $0.44 input and $1.50 output per 1M tokens, billed pay-per-use from your credit balance with no subscription.
GLM 5.3 FlashX 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 FlashX
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.
OpenAI-compatible
Drop-in with any OpenAI SDK. Change the base URL and key, keep your code.
Specifications
- Modality
- chat
- Context window
- 1000K tokens
- Max output
- 65.5K tokens
- Streaming
- Yes
- Tool / function calling
- Yes
- Vision input
- —
GLM 5.3 FlashX pricing
- A million tokens in and a million out costs $1.94 here, all-in.
- That makes it the 21st cheapest of the 81 chat models we serve, ranked on output price.
- It runs 3.5× cheaper than GLM 5.3, the pricier option from the same maker.
Getting started with GLM 5.3 FlashX
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-flashx",
messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)GLM 5.3 FlashX use cases
What teams build with GLM 5.3 FlashX 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 FlashX 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 FlashX vs Claude Opus 4.7
Compare GLM 5.3 FlashX 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 FlashX vs GPT-5.5
Compare GLM 5.3 FlashX 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 FlashX vs Gemini 3.1 Pro Preview
Compare GLM 5.3 FlashX 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 FlashX API: FAQ
How do I call GLM 5.3 FlashX 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-flashx`. 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 FlashX cost on ApexApi?
$0.44 per million input tokens and $1.50 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 FlashX?
1,000,000 tokens. It can return up to 65,536 tokens in a single response.
Does GLM 5.3 FlashX support tool calling and image input?
GLM 5.3 FlashX supports tool / function calling and streaming responses, and it does not support image (vision) input.
What should I use instead of GLM 5.3 FlashX?
From the same maker, GLM 5.3 Flash costs less for lighter work and GLM 4.7 is the step up when this one falls short. Switching is one string: both run on the same endpoint and the same key, so there is nothing to re-integrate.
Ready to build with GLM 5.3 FlashX?
One API key. Every major AI model. Pay only for what you use.
Try GLM 5.3 FlashX, pay as you go from $5