Which is cheaper, GPT-5.5 and GLM-5.3?

GLM-5.3 has the lowest input price. Per 1M input tokens: GPT-5.5 from $5.00 and GLM-5.3 from $0.56.

Which has the larger context window, GPT-5.5 and GLM-5.3?

GPT-5.5 has the largest context window: GPT-5.5 1,050,000 tokens and GLM-5.3 1,048,576 tokens.

Which is better for coding, GPT-5.5 and GLM-5.3?

GPT-5.5 scores highest on the Artificial Analysis Coding Index: GPT-5.5 74.9 and GLM-5.3 74.8.

Can I switch between GPT-5.5 and GLM-5.3 without changing my code?

Yes. All of them are served through FastRouter's OpenAI-compatible API, so switching is a change of the model parameter (openai/gpt-5.5, z-ai/glm-5.3).

GPT-5.5 vs GLM-5.3

Side-by-side pricing per provider, context window, benchmark scores and speed, all on one OpenAI-compatible API.

GPT-5.5 OpenAIopenai/gpt-5.5

GLM-5.3 Z.aiz-ai/glm-5.3

Creator

OpenAI

Z.ai

Released

Apr 24, 2026

Aug 18, 2026

Context window

1.05M

Max output

128K

131K

Input / 1MLowest provider price

$5.00$5.00–$5.50 across 2

$0.56$0.56–$1.40 across 5

Output / 1MLowest provider price

$30.00$30.00–$33.00 across 2

$2.50$2.50–$4.40 across 5

Providers

IntelligenceArtificial Analysis index

38.4

44.8

CodingArtificial Analysis index

74.9

74.8

LatencyMedian time to first token

6.1s

—

ThroughputMedian tokens per second

<1 t/s

—

Accepts

Files, Image, Text

Text

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

GPT-5.5 vs GLM-5.3: summary

GPT-5.5 and GLM-5.3 are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

GPT-5.5, from OpenAI, has a 1,050,000-token context window, costs from $5.00/1M input and $30.00/1M output tokens across 2 providers and scores 38.4 on the Artificial Analysis Intelligence Index.

GLM-5.3, from Z.ai, has a 1,048,576-token context window, costs from $0.56/1M input and $2.50/1M output tokens across 5 providers and scores 44.8 on the Artificial Analysis Intelligence Index.

GLM-5.3 is the cheapest on input, 8.9× cheaper than the next model, GPT-5.5 has the largest context window, GLM-5.3 scores highest for intelligence and GPT-5.5 leads on coding.

Switch with one line

client = OpenAI(base_url="https://api.fastrouter.ai/api/v1", api_key="<FASTROUTER_API_KEY>") client.chat.completions.create(model="openai/gpt-5.5", messages=[...]) # or client.chat.completions.create(model="z-ai/glm-5.3", messages=[...])

Full API docs

Frequently asked questions

More comparisons

Benchmark scores sourced from ArtificialAnalysis