Gemini 2.5 Flash vs GPT-5 Mini
Gemini 2.5 Flash and GPT-5 Mini are both positioned as the low-cost, high-throughput tier from their labs — Google's workhorse reasoning model versus OpenAI's compact GPT-5 variant. They shipped two months apart (June 17 vs August 7, 2025) and compete on the same price band. The real differences show up in context window size, input modalities, and how each performs across Design Arena's coding and UI benchmarks. Both are available on OpenKey with one API key and a flat 3% fee over provider list price.
Spec vs spec
| Spec | Gemini 2.5 Flash | GPT-5 Mini |
|---|---|---|
| Context window | 1.0M | 400K |
| Max output | 66K | 128K |
| Input modalities | file, image, text, audio, video | text, image, file |
| Output modalities | text | text |
| Knowledge cutoff | Jan 31, 2025 | May 31, 2024 |
| Released | Jun 17, 2025 | Aug 7, 2025 |
| Reasoning | optional | always on |
Pricing
Per 1M tokens. Provider price plus the flat 3% fee — the sum is what you pay.
google/gemini-2.5-flash
Input · 1M tokens
$0.300 + 3%$0.309
Output · 1M tokens
$2.50 + 3%$2.58
Cache read · 1M tokens
$0.030 + 3%$0.031
Cache write · 1M tokens
$0.083 + 3%$0.086
FEE — FLAT, EVERY MODEL3%
openai/gpt-5-mini
Input · 1M tokens
$0.250 + 3%$0.258
Output · 1M tokens
$2.00 + 3%$2.06
Cache read · 1M tokens
$0.025 + 3%$0.026
FEE — FLAT, EVERY MODEL3%
One workload, priced on both
10M input + 2M output tokens at each model's price, flat 3% fee included.
google/gemini-2.5-flash
$8.24
$8.00 provider + 3%
openai/gpt-5-miniCheaper
$6.70
$6.50 provider + 3%
Benchmarks
Design Arena categories where both models have results. Higher Elo and lower rank win.
| Gemini 2.5 Flash | GPT-5 Mini | |||
|---|---|---|---|---|
| Category | Elo | Rank | Elo | Rank |
| 3D | 1148 | #64 | 1114 | #73 |
| Code | 1153 | #69 | 1164 | #64 |
| Data viz | 1171 | #58 | 1167 | #62 |
| Game dev | 1131 | #72 | 1194 | #54 |
| SVG | 1078 | #58 | 1149 | #42 |
| UI components | 1148 | #63 | 1161 | #57 |
| Websites | 1158 | #68 | 1167 | #62 |
Head-to-head preference voting. How we filter and rank
Pricing on a real workload
On OpenKey, Gemini 2.5 Flash costs $0.309/M input and $2.575/M output (provider list $0.30/$2.50, ×1.03 fee). GPT-5 Mini costs $0.2575/M input and $2.06/M output (provider list $0.25/$2.00, ×1.03). For a 10M-input, 2M-output workload — a reasonable size for a coding agent session or batch job — Gemini 2.5 Flash runs $8.00 and GPT-5 Mini runs $6.50. That's a 23% cost gap in GPT-5 Mini's favor on this workload shape, driven mostly by the completion price: Gemini's output is 2.575 vs GPT-5 Mini's 2.06, a 1.2x input-price ratio and a similar spread on output. Gemini also has a cache-write price ($0.083333/M) that GPT-5 Mini's provider data doesn't list, so repeated-context workloads may narrow the gap further in Gemini's favor if you're hitting cache reads at $0.03/M vs GPT-5 Mini's $0.025/M.
Coding and UI benchmarks (Design Arena)
Across the categories both models are ranked in, GPT-5 Mini leads on codecategories (1164 elo, rank 64 vs Gemini's 1153, rank 69), dataviz (1167 vs 1171 — Gemini edges this one), gamedev (1194 vs 1131 — GPT-5 Mini's biggest margin), svg (1149 vs 1078), uicomponent (1161 vs 1148), and website (1167 vs 1158). Gemini only wins outright on dataviz. GPT-5 Mini also has an asciiart score (1173 elo, rank 33) with no Gemini equivalent in this data. If you're picking a model for a coding agent or a UI-generation pipeline, GPT-5 Mini's benchmark spread is the stronger signal.
Context window and modalities
Gemini 2.5 Flash's 1,048,576-token context is 2.62x GPT-5 Mini's 400,000. If you're feeding full codebases, long transcripts, or multi-document RAG contexts without chunking, that gap matters. Gemini also accepts audio and video input on top of text, image, and file — GPT-5 Mini is limited to text, image, and file. On the output side, GPT-5 Mini allows up to 128,000 completion tokens versus Gemini's 65,535, useful if you need very long generated output in a single call. Both return text only.
Reasoning and tokenizer differences
GPT-5 Mini's reasoning is mandatory — you choose an effort level (high, medium, low, minimal; default medium) and it always uses its GPT tokenizer. Gemini 2.5 Flash's reasoning is optional, controlled via `include_reasoning`/`reasoning` parameters, using the Gemini tokenizer. GPT-5 Mini's knowledge cutoff is 2024-05-31; Gemini 2.5 Flash's is more recent at 2025-01-31, which matters if you need fresher world knowledge without retrieval.
Which model for which job
| Use case | Pick | Why |
|---|---|---|
| Long-document or video analysis | Gemini 2.5 Flash | 1,048,576-token context (2.62x GPT-5 Mini's) plus native audio/video input |
| Coding agent / codegen pipeline | GPT-5 Mini | Higher Design Arena elo in codecategories (1164 vs 1153) and gamedev (1194 vs 1131) |
| Cost-sensitive high-volume workload | GPT-5 Mini | $6.50 vs $8.00 on a 10M-in/2M-out workload |
| UI component generation | GPT-5 Mini | 1161 elo vs Gemini's 1148 in uicomponent category |
| Data visualization tasks | Gemini 2.5 Flash | 1171 elo vs GPT-5 Mini's 1167 in dataviz — Gemini's only category win |
| Freshest knowledge without retrieval | Gemini 2.5 Flash | Knowledge cutoff 2025-01-31 vs GPT-5 Mini's 2024-05-31 |
Questions
- Which is cheaper, Gemini 2.5 Flash or GPT-5 Mini?
- GPT-5 Mini is cheaper on OpenKey: $0.2575/M input and $2.06/M output versus Gemini 2.5 Flash's $0.309/M input and $2.575/M output. On a 10M-input/2M-output workload, that's $6.50 for GPT-5 Mini against $8.00 for Gemini 2.5 Flash.
- Which has the bigger context window?
- Gemini 2.5 Flash supports 1,048,576 tokens of context, 2.62x GPT-5 Mini's 400,000. GPT-5 Mini compensates with a larger max output at 128,000 tokens versus Gemini's 65,535.
- Which model wins more Design Arena categories?
- GPT-5 Mini leads in codecategories (1164 vs 1153), gamedev (1194 vs 1131), svg (1149 vs 1078), uicomponent (1161 vs 1148), and website (1167 vs 1158). Gemini 2.5 Flash only wins dataviz, 1171 vs 1167.
- Does either model support audio or video input?
- Gemini 2.5 Flash does — its input modalities include audio and video alongside text, image, and file. GPT-5 Mini's inputs are limited to text, image, and file, with no audio or video support in this data.