Gemini 2.5 Flash Lite to Gemini 3.5 Flash Lite Migration Guide & Comparison
Gemini 2.5 Flash Lite vs Gemini 3.5 Flash Lite: which should I use?
Gemini 3.5 Flash Lite costs 3.2× more per blended million tokens than Gemini 2.5 Flash Lite. Gemini 2.5 Flash Lite has the larger context window (1,000,000 tokens). Default to Gemini 2.5 Flash Lite unless you specifically need Gemini 3.5 Flash Lite's edge.
Price, speed, and task evidence
Task verdict
Best-fit task signals from the published model strengths; this is not a substitute for a controlled benchmark.
| Fact | Gemini 2.5 Flash Lite | Gemini 3.5 Flash Lite |
|---|---|---|
| Best fit | Legacy high-volume Gemini tasks superseded by 3.5 Flash Lite. | High-volume tasks that still need long-context handling on a tight budget. |
| Reasoning mode | Unavailable | Unavailable |
Effective workload cost
Modeled for Coding Agent: 20,000 input + 2,000 output tokens per task, 1 turn. This is a workload model, not a provider quote.
| Fact | Gemini 2.5 Flash Lite | Gemini 3.5 Flash Lite |
|---|---|---|
| Coding Agent / task | $0.0028 (modeled) (winner) | $0.0080 (modeled) |
| Input / output rate | $0.10 / $0.40 per M | $0.25 / $1.50 per M |
Speed
Only non-estimated benchmark results are shown as measured.
| Fact | Gemini 2.5 Flash Lite | Gemini 3.5 Flash Lite |
|---|---|---|
| Measured throughput | Unavailable | 162 tokens/s |
| Time to first token | Unavailable | 240 ms |
API compatibility
Provider-level wire-format and SDK facts; model-specific parameter differences may still apply.
| Fact | Gemini 2.5 Flash Lite | Gemini 3.5 Flash Lite |
|---|---|---|
| OpenAI SDK | Not drop-in | Not drop-in |
| Request shape | contents/parts structure instead of messages; an OpenAI-compatible endpoint exists but only covers a subset of parameters. | contents/parts structure instead of messages; an OpenAI-compatible endpoint exists but only covers a subset of parameters. |
| Streaming | SSE (Gemini streamGenerateContent) | SSE (Gemini streamGenerateContent) |
Privacy and retention
Provider policy and residency facts from the verified provider registry. A missing retention policy is not treated as a guarantee.
| Fact | Gemini 2.5 Flash Lite | Gemini 3.5 Flash Lite |
|---|---|---|
| Provider says API data trains models | No | No |
| Published retention period | Unavailable | Unavailable |
| Data residency | Global by default; Vertex AI offers selectable regional endpoints | Global by default; Vertex AI offers selectable regional endpoints |
Migration effort
Direction is from each displayed model to the other. Effort is derived from provider compatibility and published parameter maps.
| Fact | Gemini 2.5 Flash Lite | Gemini 3.5 Flash Lite |
|---|---|---|
| Move Gemini 2.5 Flash Lite → Gemini 3.5 Flash Lite | drop-in; 0 breaking parameter differences | Target: Gemini 3.5 Flash Lite |
| Move Gemini 3.5 Flash Lite → Gemini 2.5 Flash Lite | Source: Gemini 3.5 Flash Lite | drop-in; 0 breaking parameter differences |
| Why | Same provider; only the model identifier changes. | Same provider; only the model identifier changes. |
Spec comparison
| Gemini 2.5 Flash Lite | Gemini 3.5 Flash Lite | |
|---|---|---|
| Price (input) | $0.10/M ✓ | $0.25/M |
| Price (output) | $0.40/M ✓ | $1.50/M |
| Blended price | $0.18/M ✓ | $0.56/M |
| Context window | 1,000,000 tokens | 1,000,000 tokens |
| Max output | 8,192 tokens | 32,000 tokens ✓ |
| Modalities | text, vision | text, vision |
| Reasoning mode | No | No |
| Released | 2025-05 | 2026-04 |
| Speed | Not measured | 162 t/s |
Cost at scale (3:1 blended)
| Tokens / month | Gemini 2.5 Flash Lite | Gemini 3.5 Flash Lite | Delta |
|---|---|---|---|
| 1,000,000 | $0.18 | $0.56 | $0.39 (3.2×) |
| 10,000,000 | $1.75 | $5.63 | $3.88 (3.2×) |
| 100,000,000 | $17.50 | $56.25 | $38.75 (3.2×) |
Choose Gemini 2.5 Flash Lite if…
- ✓Ultra-low cost legacy model
- ✓1M context window
- ✓Fast completions
- ✓Legacy high-volume Gemini tasks superseded by 3.5 Flash Lite.
Choose Gemini 3.5 Flash Lite if…
- ✓Cheapest Gemini with a 1M-token context window
- ✓Faster and cheaper than 3.1 Flash Lite
- ✓Vision input included
- ✓High-volume tasks that still need long-context handling on a tight budget.
Run this exact matchup right now
Send the same prompt to Gemini 2.5 Flash Lite and Gemini 3.5 Flash Lite side by side and see the outputs yourself.
Try Gemini 2.5 Flash Lite vs Gemini 3.5 Flash Lite FreeFAQ
Is Gemini 2.5 Flash Lite cheaper than Gemini 3.5 Flash Lite?
Gemini 2.5 Flash Lite is cheaper, at $0.18 per million blended tokens vs $0.56 for Gemini 3.5 Flash Lite.
Which has the bigger context window, Gemini 2.5 Flash Lite or Gemini 3.5 Flash Lite?
Both models support 1,000,000 tokens of context.
Can Gemini 2.5 Flash Lite replace Gemini 3.5 Flash Lite for coding?
Both are viable for coding. Ultra-low cost legacy model (Gemini 2.5 Flash Lite) vs Cheapest Gemini with a 1M-token context window (Gemini 3.5 Flash Lite) — pick based on which strength matters more for your workload.
Related
Pricing verified 2026-04-06. Specs verified 2026-08-08.