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GLM 5.3 Flash vs GPT-5.5

Updated October 21, 2026. 94 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace GLM 5.3 Flash Replace GPT-5.5
GLM 5.3 FlashZ.ai
Coding
71.0
Overall
41.8
Output $/M
$0.50
36
GPT-5.5OpenAI
Coding
67.8
Overall
38.4
Output $/M
$30.00
58
vs boards won of 94 shared

Decision reading

Pick GLM 5.3 Flash for coding: it scores 71.0 on the Vibe Coding Index against 67.8 for GPT-5.5.

Pick GPT-5.5 when the context window is larger, 1.05M against 1.05M tokens, or when what matters is LiveBench coding or AA Coding Index, where it leads.

Model AGLM 5.3 FlashZ.ai71.0/1002 independent benchmarks$0.02 per solved taskModel BGPT-5.5OpenAI67.8/1002 independent benchmarks$1.65 per solved task
Shared results
94
GLM 5.3 Flash only
8
GPT-5.5 only
38
Like-for-like categories
8 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

At a glance

Coding index
GLM 5.3 Flash 71.0 from 2 benchmarks, GPT-5.5 67.8 from 2 benchmarks.
Widest category
Math, 21.0 points apart on average over 6 shared benchmarks.
Widest single gap
FrontierMath, tier 4: GLM 5.3 Flash 17.1% against GPT-5.5 72.5%, 55.4 points apart on a 0 to 100 scale.
Output price
GLM 5.3 Flash $0.50 against GPT-5.5 $30.00 per million output tokens, 60.0x apart.
Context window
GLM 5.3 Flash takes 1.05M tokens, GPT-5.5 1.05M.

Benchmark by benchmark

First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.

Boards won, where both have a result
CategoryGLM 5.3 FlashBarsGPT-5.5Ties
Coding711
Intelligence11
Agentic work64
Reasoning312
Math33
Knowledge25
Web design72
General720
All shared boards3658
CodingLike-for-likeFour of these boards feed the Vibe Coding Index711
Coding benchmarks for GLM 5.3 Flash and GPT-5.5
BenchmarkGLM 5.3 FlashGPT-5.5Leader
LiveBench coding80.6%85.1%GPT-5.5
LMArena WebDev16071513GLM 5.3 Flash
AA Coding Index71.574.9GPT-5.5
LiveCodeBench (Vals AI)80.5%85.3%GPT-5.5
SWE-bench Verified (Vals AI)92.0%82.6%GLM 5.3 Flash
Terminal-Bench 4 (Vals AI)37.4%Not measuredOnly GLM 5.3 Flash measured
Vibe Code Bench (Vals AI)30.8%69.8%GPT-5.5
Code migration (Vals AI)20.5%45.2%GPT-5.5
ProgramBench (Vals AI)0.0%0.5%GPT-5.5
IOI (Vals AI)52.5%Not measuredOnly GLM 5.3 Flash measured
Terminal-Bench 2.1 (Vals AI)62.9%76.4%GPT-5.5
Vibe Code Bench 1-100 (Vals AI)16.0%Not measuredOnly GLM 5.3 Flash measured
SkillsBench (Vals AI)40.2%62.5%GPT-5.5
CyberBench (Vals AI)67.9%Not measuredOnly GLM 5.3 Flash measured
SciCode51.6%56.1%GPT-5.5
Terminal-Bench Hard (Artificial Analysis run)Not measured60.6%Only GPT-5.5 measured
Terminal-BenchNot measured84.7%Only GPT-5.5 measured
FrontierCode31.8%43.0%GPT-5.5
FrontierSWE18.1%Not measuredOnly GLM 5.3 Flash measured
GSO-BenchNot measured40.2%Only GPT-5.5 measured
WeirdMLNot measured84.9%Only GPT-5.5 measured
MirrorCodeNot measured10.0%Only GPT-5.5 measured
ALE-Bench303.61943.0GPT-5.5
LMArena Text: coding15071494GLM 5.3 Flash
LMArena Text: software and IT15001493GLM 5.3 Flash
LMArena WebDev: React16241506GLM 5.3 Flash
LMArena WebDev: HTML15771543GLM 5.3 Flash
LMArena WebDev: from an image15781532GLM 5.3 Flash
Neither model has a result on the other 10 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index11
Intelligence benchmarks for GLM 5.3 Flash and GPT-5.5
BenchmarkGLM 5.3 FlashGPT-5.5Leader
AA Intelligence Index41.838.4GLM 5.3 Flash
Epoch Capabilities Index153.1159.7GPT-5.5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index64
Agentic work benchmarks for GLM 5.3 Flash and GPT-5.5
BenchmarkGLM 5.3 FlashGPT-5.5Leader
AA Agentic Index50.936.4GLM 5.3 Flash
Design Arena: agents building web appsNot measured1117Only GPT-5.5 measured
Design Arena: agents building full-stack appsNot measured1089Only GPT-5.5 measured
Design Arena: agents building mobile appsNot measured1143Only GPT-5.5 measured
Design Arena: agents building Android appsNot measured1169Only GPT-5.5 measured
Design Arena: agents building Godot gamesNot measured1173Only GPT-5.5 measured
Design Arena: agents building gamesNot measured1179Only GPT-5.5 measured
Design Arena: HTML slidesNot measured1067Only GPT-5.5 measured
Design Arena: PowerPoint slidesNot measured1108Only GPT-5.5 measured
LiveBench research70.1%61.6%GLM 5.3 Flash
LiveBench browser84.0%48.0%GLM 5.3 Flash
LiveBench long agentic28.4%44.6%GPT-5.5
SREBench (Vals AI)0.8%3.8%GPT-5.5
Finance Agent (Vals AI)57.9%51.8%GLM 5.3 Flash
Tax Agent Bench (Vals AI)31.6%21.8%GLM 5.3 Flash
Legal Research Bench (Vals AI)45.2%40.4%GLM 5.3 Flash
Harvey's Legal Agent Benchmark (Vals AI)10.4%Not measuredOnly GLM 5.3 Flash measured
Excel Modeling Benchmark (Vals AI)55.9%64.5%GPT-5.5
Terminal-Bench-Science (Vals AI)2.9%Not measuredOnly GLM 5.3 Flash measured
Time Horizon Index (Vals AI)Not measured8.3%Only GPT-5.5 measured
τ²-Bench TelecomNot measured93.9%Only GPT-5.5 measured
APEX-Agents52.8%55.1%GPT-5.5
Remote Labor IndexNot measured6.3%Only GPT-5.5 measured
OSWorld 2.0Not measured13.0%Only GPT-5.5 measured
DeepResearch BenchNot measured54.0%Only GPT-5.5 measured
PostTrainBenchNot measured27.2%Only GPT-5.5 measured
Vending-Bench 2Not measured$7,524Only GPT-5.5 measured
Neither model has a result on the other 12 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index312
Reasoning benchmarks for GLM 5.3 Flash and GPT-5.5
BenchmarkGLM 5.3 FlashGPT-5.5Leader
GPQA Diamond86.4%93.2%GPT-5.5
LiveBench reasoning77.6%89.7%GPT-5.5
MMMU Pro (Vals AI)86.0%88.3%GPT-5.5
GPQA Diamond (Artificial Analysis run)91.2%93.5%GPT-5.5
Humanity's Last Exam (Artificial Analysis run)39.9%45.8%GPT-5.5
GPQA Diamond (Epoch AI run)90.2%90.7%GPT-5.5
ARC-AGI91.0%95.0%GPT-5.5
ARC-AGI-265.8%85.0%GPT-5.5
SimpleBenchNot measured69.0%Only GPT-5.5 measured
Chess puzzles21.0%63.0%GPT-5.5
Mystery game puzzles8.0%56.0%GPT-5.5
EBR-benchNot measured34.3%Only GPT-5.5 measured
LMArena Text: hard prompts14901489GLM 5.3 Flash
LMArena Text: expert15111507GLM 5.3 Flash
LMArena Text: hard prompts in English14881483GLM 5.3 Flash
LMArena Vision: diagrams13171325GPT-5.5
LMArena Vision: homework13181332GPT-5.5
Neither model has a result on the other 4 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index33
Math benchmarks for GLM 5.3 Flash and GPT-5.5
BenchmarkGLM 5.3 FlashGPT-5.5Leader
OTIS Mock AIME93.9%84.4%GLM 5.3 Flash
FrontierMath, tiers 1 to 355.8%85.3%GPT-5.5
FrontierMath, tier 417.1%72.5%GPT-5.5
ProofBench21.0%50.0%GPT-5.5
LMArena Text: math15031487GLM 5.3 Flash
LMArena Text: mathematical work14971496GLM 5.3 Flash
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index25
Knowledge benchmarks for GLM 5.3 Flash and GPT-5.5
BenchmarkGLM 5.3 FlashGPT-5.5Leader
MMLU Pro86.1%88.1%GPT-5.5
LegalBench (Vals AI)83.9%86.5%GPT-5.5
CaseLaw (Vals AI)Not measured66.2%Only GPT-5.5 measured
CorpFin (Vals AI)Not measured68.4%Only GPT-5.5 measured
TaxEval (Vals AI)75.6%75.0%GLM 5.3 Flash
MortgageTax (Vals AI)Not measured68.8%Only GPT-5.5 measured
MedCode (Vals AI)Not measured49.1%Only GPT-5.5 measured
SimpleQA VerifiedNot measured63.0%Only GPT-5.5 measured
LMArena Text: science14841485GPT-5.5
LMArena Text: medicine and healthcare14751465GLM 5.3 Flash
LMArena Text: legal and government14731491GPT-5.5
LMArena Text: business and finance14601478GPT-5.5
Neither model has a result on the other 5 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index72
Web design benchmarks for GLM 5.3 Flash and GPT-5.5
BenchmarkGLM 5.3 FlashGPT-5.5Leader
Design Arena: websites12721256GLM 5.3 Flash
Design Arena: UI components13161260GLM 5.3 Flash
Design Arena: game dev12791294GPT-5.5
Design Arena: data viz12621265GPT-5.5
Design Arena: 3D13161198GLM 5.3 Flash
Design Arena: all code categories12821260GLM 5.3 Flash
Design Arena: SVG12841234GLM 5.3 Flash
Design Arena: ASCII art12691254GLM 5.3 Flash
LiveBench design77.2%70.3%GLM 5.3 Flash
GeneralLike-for-likePublic boards, shown as published, kept out of the index720
General benchmarks for GLM 5.3 Flash and GPT-5.5
BenchmarkGLM 5.3 FlashGPT-5.5Leader
Vals Index50.9%Not measuredOnly GLM 5.3 Flash measured
LiveBench data analysis76.4%81.6%GPT-5.5
Public Benefits Bench (Vals AI)Not measured60.9%Only GPT-5.5 measured
SAGE (Vals AI)Not measured51.5%Only GPT-5.5 measured
MedScribe (Vals AI)88.9%86.9%GLM 5.3 Flash
Vals Multimodal IndexNot measured68.1%Only GPT-5.5 measured
IFBenchNot measured75.9%Only GPT-5.5 measured
Long context reasoning (AA-LCR)80.0%84.3%GPT-5.5
DTBenchNot measured96.0%Only GPT-5.5 measured
LMCANot measured54.3%Only GPT-5.5 measured
Surface Evolver Bench52.5%88.1%GPT-5.5
Furniture assemblyNot measured44.2%Only GPT-5.5 measured
ExploitBenchNot measured47.4%Only GPT-5.5 measured
CL-bench LifeNot measured22.2%Only GPT-5.5 measured
LMArena Text14711471GLM 5.3 Flash
LMArena Text: instruction following14781478GPT-5.5
LMArena Text: creative writing14411455GPT-5.5
LMArena Vision12941297GPT-5.5
LMArena Text: English14741470GLM 5.3 Flash
LMArena Text: non-English14621467GPT-5.5
LMArena Text: Chinese15311534GPT-5.5
LMArena Text: German14621480GPT-5.5
LMArena Text: Japanese14441499GPT-5.5
LMArena Text: Korean14361460GPT-5.5
LMArena Text: French14911485GLM 5.3 Flash
LMArena Text: Spanish14751468GLM 5.3 Flash
LMArena Text: Russian14651473GPT-5.5
LMArena Text: Polish14501465GPT-5.5
LMArena Text: multi-turn14691476GPT-5.5
LMArena Text: longer queries14811484GPT-5.5
LMArena Text: writing and language14551466GPT-5.5
LMArena Text: entertainment and media14401449GPT-5.5
LMArena Vision: English12951292GLM 5.3 Flash
LMArena Vision: Chinese13631360GLM 5.3 Flash
LMArena Vision: reading text12991306GPT-5.5
LMArena Vision: humor12791293GPT-5.5
LMArena Vision: recognizing thingsNot measured1231Only GPT-5.5 measured
LMArena Vision: creative writing12701301GPT-5.5
LMArena DocumentNot measured1486Only GPT-5.5 measured
Neither model has a result on the other 7 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GLM 5.3 Flash and GPT-5.5
BenchmarkGLM 5.3 FlashGPT-5.5Leader
Neither model has a result on 5 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

GLM 5.3 Flash$0.0004Fits in one request
GPT-5.5$0.020Fits in one request

GLM 5.3 Flash costs less

Repository review

50K input + 3K output tokens

GLM 5.3 Flash$0.0090Fits in one request
GPT-5.5$0.340Fits in one request

GLM 5.3 Flash costs less

Agent loop

200K input + 10K output tokens

GLM 5.3 Flash$0.035Fits in one request
GPT-5.5$1.30Fits in one request

GLM 5.3 Flash costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of GLM 5.3 Flash and GPT-5.5
SpecificationZ.ai GLM 5.3 FlashOpenAI GPT-5.5
MakerZ.aiOpenAI
WeightsOpen weightsNo public weights listed
ReleasedAugust 26, 2026April 24, 2026
Context window1.05M1.05M
Input $/Mtok$0.15$5.00
Output $/Mtok$0.50$30.00
Coding index71.067.8
Independent measurements behind it22
Cost per solved task$0.02$1.65
SourceOpenRouter listingOpenRouter listing

Questions

Is GLM 5.3 Flash better than GPT-5.5 for coding?

Pick GLM 5.3 Flash for coding: it scores 71.0 on the Vibe Coding Index against 67.8 for GPT-5.5. Pick GPT-5.5 when the context window is larger, 1.05M against 1.05M tokens, or when what matters is LiveBench coding or AA Coding Index, where it leads.

Which is cheaper, GLM 5.3 Flash or GPT-5.5?

GLM 5.3 Flash costs $0.15 per million input tokens and $0.50 per million output tokens; GPT-5.5 costs $5.00 and $30.00. Per solved SWE-bench Verified task, GLM 5.3 Flash costs $0.02 and GPT-5.5 $1.65.

Which has the bigger context window, GLM 5.3 Flash or GPT-5.5?

GPT-5.5, with 1.05M tokens against 1.05M.

How many benchmarks is the GLM 5.3 Flash vs GPT-5.5 comparison based on?

94 benchmarks have a result for both models as of October 21, 2026. GLM 5.3 Flash's coding index rests on 2 independent benchmarks and GPT-5.5's on 2. Where only one model has a result, the page says so instead of naming a winner.

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