ZMIME
Comparison · 2 models · Updated Oct 4, 2026

Claude Sonnet 5.5 vs GLM-5.3-Flash

GLM-5.3-Flash comes out ahead, 80 to 72 on our weighted score, and it is the cheaper option too.

  1. Anthropic

    Claude Sonnet 5.5

    Released Sep 28, 2026

    72/100
    • ECI165.2
    • Price$2.00 / $10.00
    • Context1M
    Full specs Remove Claude Sonnet 5.5
  2. Our pick

    Z.ai (Zhipu)

    GLM-5.3-Flash

    Released Aug 26, 2026

    80/100
    • ECI151.9
    • Price$0.15 / $0.50
    • Context1M
    Full specs Remove GLM-5.3-Flash

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

GLM-5.3-Flash is our pick

GLM-5.3-Flash is the better all-round choice, scoring 80/100 against Claude Sonnet 5.5 (72). It leads on price and inputs & features. Claude Sonnet 5.5 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityClaude Sonnet 5.5Capabilities Index (ECI): Claude Sonnet 5.5 165.2 · GLM-5.3-Flash 151.9
  • Lowest priceGLM-5.3-FlashGLM-5.3-Flash $0.237 · Claude Sonnet 5.5 $4.00 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameClaude Sonnet 5.5 1,000,000 · GLM-5.3-Flash 1,000,000 tokens
  • Widest inputsGLM-5.3-FlashClaude Sonnet 5.5: Text, Images, PDFs · GLM-5.3-Flash: Text, Images, PDFs, Video
  • Self-hostingGLM-5.3-FlashPublishes downloadable weights
How the score is built
MeasureWeightClaude Sonnet 5.5GLM-5.3-Flash
CapabilityCapabilities Index (ECI)50%9781
Price25%2179
Inputs & features15%8090
Context window10%6060
Overall100%72/10080/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

Claude Sonnet 5.5 vs GLM-5.3-Flash specifications side by side
SpecificationClaude Sonnet 5.5AnthropicGLM-5.3-FlashZ.ai (Zhipu)
Capability
Capabilities Index (ECI)165.2 (best)151.9
ECI rank#3 of 148 (best)#42 of 148
GPQA DiamondGraduate-level science questions95.6% (best)90.2%
FrontierMath Tiers 1–3Research-level mathematics88.8% (best)55.8%
OTIS Mock AIME 2024–2025Competition mathematics100% (best)93.9%
SimpleQA VerifiedShort factual questions46.5%—
Price per million tokens
Input$2.00$0.15 (best)
Output$10.00$0.50 (best)
Cached input$0.20$0.03 (best)
Blended (3:1)$4.00$0.237 (best)
Long-context rateSame rateSame rate
Price sourceOfficial Anthropic APIOfficial Z.AI API
Limits
Context window1,000,000 tokens1,000,000 tokens
Max output128,000 tokens131,072 tokens (best)
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoNoYes
ReasoningYeslow · medium · high · xhigh · maxYeslow · high · max
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryOpen
API model IDclaude-sonnet-5-5glm-5.3-flash
API providers2365 (best)
ReleasedSep 28, 2026Aug 26, 2026
Knowledge cutoffJun 2026—
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • Claude Sonnet 5.5$40.00
  • GLM-5.3-Flash$2.50
04 — Questions

Which should you choose?

Which is better: Claude Sonnet 5.5 or GLM-5.3-Flash?

GLM-5.3-Flash is the better all-round choice, scoring 80/100 against Claude Sonnet 5.5 (72). It leads on price and inputs & features. Claude Sonnet 5.5 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Sonnet 5.5 or GLM-5.3-Flash?

GLM-5.3-Flash is cheaper at $0.15 input / $0.50 output per million tokens (official Z.AI API price). Claude Sonnet 5.5 costs $2.00 input / $10.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $0.237 per million tokens for GLM-5.3-Flash versus $4.00 for Claude Sonnet 5.5 (17× as much).

Which scores higher on benchmarks?

Claude Sonnet 5.5 scores higher on the Capabilities Index (ECI): Claude Sonnet 5.5 165.2 (#3 of 148) and GLM-5.3-Flash 151.9 (#42 of 148). Their confidence ranges do not overlap (161.8–169.4 vs 149.4–154.3), so the gap is a real one. On individual benchmarks: GPQA Diamond — Claude Sonnet 5.5 95.6%, GLM-5.3-Flash 90.2%; FrontierMath Tiers 1–3 — Claude Sonnet 5.5 88.8%, GLM-5.3-Flash 55.8%; OTIS Mock AIME 2024–2025 — Claude Sonnet 5.5 100%, GLM-5.3-Flash 93.9%.

Which is better for coding?

There are no published SWE-bench Verified results for Claude Sonnet 5.5 and GLM-5.3-Flash yet, so there is no like-for-like coding score. On overall capability, Claude Sonnet 5.5 leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

Claude Sonnet 5.5 and GLM-5.3-Flash share the same 1,000,000-token context window. Maximum output per response: Claude Sonnet 5.5 up to 128,000, GLM-5.3-Flash up to 131,072 tokens.

Which can read images, PDFs, audio or video?

Claude Sonnet 5.5 accepts text, images and PDFs; GLM-5.3-Flash accepts text, images, PDFs and video. GLM-5.3-Flash handles the widest range of inputs.

Are any of these open source?

GLM-5.3-Flash publishes its weights and can be self-hosted; Claude Sonnet 5.5 is proprietary.

Which is newer?

Claude Sonnet 5.5 is the newest, released Sep 28, 2026. GLM-5.3-Flash came out Aug 26, 2026. Knowledge cutoff: Claude Sonnet 5.5 Jun 2026.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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