GLM 5.3 Free
TL;DR: GLM 5.3 is Z.ai's newest flagship model (announced August 2026), built on the GLM 5.2 base with a large long-horizon post-training push. It offers a 1M-token context, 128K maximum output, and always-on reasoning. You can chat with GLM 5.3 free on glm5.app today — new users get free credits with no credit card. The model API, pricing, and open weights are still pending, so this article separates confirmed facts from unconfirmed details.
Why GLM 5.3 is getting attention right now
A new flagship model is easy to announce and hard to evaluate: blog posts repeat specs within hours, and nobody agrees on what is real, what is rumored, or how to actually try it. That is exactly where GLM 5.3 sits as of August 2026.
Z.ai has confirmed the model and core specs through official channels, and the GLM Coding Plan has rolled it out. But the public API is "coming soon," so most coverage is spec repetition or rumor. This article draws on Z.ai's official docs and blog, Z.ai's Hugging Face releases, and the glm5.app product pages, last checked August 18, 2026. Everything below is either confirmed by those sources or marked pending — nothing is guessed.
What GLM 5.3 is: the confirmed facts
GLM 5.3 is Z.ai's latest flagship model — and it is not a new base model. Z.ai states it uses the same base as GLM 5.2, with all improvements coming from post-training scaled up dramatically toward long-horizon, agent-style tasks: real compute clusters, storage systems, docs, and codebases.
| Spec | Value |
|---|---|
| Context window | 1M tokens |
| Maximum output | 128K tokens |
| Modality | Text in / text out |
| Reasoning | Always on — cannot be disabled |
| Reasoning effort levels | low, high, max (default max) |
| Base model | GLM 5.2 (changes come from post-training) |
| Official availability | GLM Coding Plan (rolled out); model API coming soon |
Reasoning always being on has two practical consequences: apps that previously disabled it must switch to enabled with a low effort level before using the glm-5.3 model ID, and the effort levels trade reasoning depth against latency and token cost — max is what Z.ai recommends for coding.
Confirmed vs. still pending
This is where most third-party articles go wrong, so let's be explicit.
Confirmed by Z.ai (as of August 2026):
- Text-only input and reasoning-only mode with three effort levels
- Benchmark results below, including a roughly 50% coding gain over GLM 5.2 on Z.ai's in-house Code Bench
- Full rollout inside the GLM Coding Plan (ZCode, Claude Code, Cline, OpenCode, and similar tools)
Pending official announcement (treat as unverified):
- Model API model ID, rate limits, and API pricing
- Open weights and license (GLM 5.2 shipped under MIT on Hugging Face, so an open release is widely expected — nothing is published yet)
- Total parameter count
If a post quotes GLM 5.3 API pricing, parameter totals, or downloadable weights, it is ahead of the official record.
GLM 5.3 benchmarks: what the numbers mean
All figures below are Z.ai-reported from its official documentation. A score applies only to the published harness and date, so treat them as a starting point and reproduce a task that resembles your own workflow before deciding.
| Benchmark | GLM 5.2 | GLM 5.3 | What it measures |
|---|---|---|---|
| Terminal-Bench 3.0 | 4.6 | 28.3 | Real terminal and CLI engineering work |
| DeepSWE v1.1 | 46.2 | 66.9 | Long-horizon software engineering |
| Agents' Last Exam | 23.8 | 28.5 | Agentic knowledge and reasoning |
| CyberGym | 77.2 | 84.5 | White-box vulnerability discovery |
The Terminal-Bench 3.0 jump — 4.6 to 28.3 — is the single largest reported gain. On CyberGym, Z.ai reports 84.5, slightly above GPT-5.6 Sol (83.6) and Mythos 5 (83.8). On Z.ai's private Code Bench, the headline is a ~50% coding gain over GLM 5.2 (34.5% at max effort on roughly 75K output tokens per task versus 23.4% at 96K). These are vendor-reported numbers, and closed-model comparisons will shift as rivals update their own benchmarks.
How to try GLM 5.3 free today
The public model API is still pending, but you do not need to wait for it.
Route 1 — Free browser chat (no credit card):
- Open the GLM 5.3 page on glm5.app or go straight to the chat app.
- Create an account — new users get free credits with no credit card required.
- Select GLM 5.3 in the model picker.
- Describe your task with constraints and a clear outcome, then refine with your own code or acceptance criteria.
This is the lowest-friction option today: reasoning, coding, and long-context work run entirely in the browser.
Route 2 — Coding-plan integrations:
If your workflow lives inside a coding agent, Z.ai's GLM Coding Plan already serves GLM 5.3 in tools like ZCode, Claude Code, Cline, and OpenCode. This is a paid subscription, not the free path, and uses a points-based quota where off-peak calls (including weekends) cost 50% of standard points.
For API builds: glm5.app exposes an OpenAI-compatible Chat Completions endpoint today, and glm-5.3 is expected to be the model ID on Z.ai's side too. Keep API keys server-side and start with a narrow request. Z.ai's docs list coming OpenAI, Responses, and Anthropic-compatible endpoints, so most codebases will only need a base-URL and model-name change.
Who GLM 5.3 is for
- Application developers building coding assistants and IDE workflows that benefit from the 1M-token context.
- Agent builders who need reasoning modes, function calling, streaming, context caching, and MCP support in long-running workflows.
- Security researchers interested in white-box code review, where Z.ai reports its strongest CyberGym result.
- Long-horizon engineering teams planning refactors across tens of thousands of lines, where effort levels balance depth against cost.
- Self-hosters watching for open weights — none published as of mid-August 2026.
FAQ
What is GLM 5.3? Z.ai's newest flagship model, announced in August 2026 — a GLM 5.2 base with much larger long-horizon post-training, a 1M-token context, and 128K maximum output.
Is GLM 5.3 free? Yes — chat with GLM 5.3 free on glm5.app, where new users get free credits without a credit card. Z.ai's own GLM Coding Plan is a paid subscription, and model API pricing has not been announced.
GLM 5.3 vs GLM 5.2: what changed? Same base model, far more post-training. Z.ai reports a ~50% coding gain on its internal Code Bench, Terminal-Bench 3.0 rising from 4.6 to 28.3, and DeepSWE v1.1 from 46.2 to 66.9.
When will the GLM 5.3 API be released? Z.ai says it is coming soon, with no firm date yet. The GLM Coding Plan already serves the model today.
Is GLM 5.3 open source? Not yet. GLM 5.2 shipped under MIT on Hugging Face, so an open release is expected, but Z.ai has not published GLM 5.3 weights or a license.
How many parameters does GLM 5.3 have? Z.ai has not published a parameter count. For context, GLM 5.2 is a 753B-parameter model on Hugging Face; GLM 5.3's totals remain unannounced.
Try GLM 5.3 free now
The fastest way to judge the GLM 5.3 hype is to run it yourself. Start a free GLM 5.3 chat on glm5.app, throw a real repository or a long debugging session at it, and compare against your current model. The official API and open weights will follow — the free browser route is available today.
Sources
- Z.ai GLM-5.3 official documentation — Official specs, benchmarks, and availability.
- Z.ai GLM-5.3 announcement blog — Official announcement and post-training details.
- Z.ai GLM-5.2 launch blog (Hugging Face) — Official write-up of the base model and June 2026 launch.
- zai-org/GLM-5.2 model card (Hugging Face) — Official model card: 753B params, MIT license, 1M context; no GLM-5.3 weights are published.
- glm5.app GLM 5.3 page — Product page for free GLM 5.3 chat and the release tracker for pending details.
Scope note: benchmark scores and the ~50% Code Bench gain are Z.ai-reported on the published harnesses. API pricing, model-ID limits, and open-weights/license details were still pending official announcements as of August 18, 2026 — verify on the official pages above before making commitments.