Introduction
TL;DR
Google released FunctionGemma on December 17, 2025—a specialized 270M parameter model based on Gemma 3 designed specifically for function calling and agentic tasks. The model translates natural language into structured function calls that execute directly on smartphones, browsers, and edge devices (Jetson Nano) with zero data transmission and 0.3-second latency. Fine-tuning boosts accuracy from 58% zero-shot baseline to 85% on production tasks. Deployment is supported across LiteRT, Ollama, vLLM, Unsloth, and Google Vertex AI, with all weights openly licensed for commercial use.
Why it matters: FunctionGemma democratizes on-device AI agents by removing cloud dependency, guaranteeing data privacy, and reducing inference costs to zero—shifting the paradigm from cloud-connected assistants to truly autonomous, private, edge-native systems.
Context: The Shift from Chat to Action
For years, conversational AI has been the dominant interface. Users ask questions; models provide answers. But as enterprises and consumers demand automation, the industry is shifting from passive chat to active agents—systems that not only talk but execute tasks.
A voice assistant that merely says “turning on the lights” is less useful than one that actually flips the switch. This requires:
- Structured output: The model must generate function schemas, not free-form text
- Local execution: For privacy and latency, this cannot go to the cloud
- Reliability: Accuracy cannot be a luxury; 85%+ correctness is mandatory for production
- Lightweight: It must fit within device memory and battery budgets
FunctionGemma addresses all four requirements, representing the production-ready convergence of edge compute and agentic AI.
What is FunctionGemma?
Core Definition
FunctionGemma is a specialized version of the Gemma 3 270M base model, fine-tuned specifically for function calling and tool use on edge devices. Unlike general-purpose language models that rely on raw text prompting to define and call functions, FunctionGemma uses dedicated formatting control tokens to reliably generate structured function calls in real-time on smartphones, laptops, and embedded systems.
Example workflow:
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Every step—parsing, function call generation, and response formatting—happens on the device, never touching external servers.
Key Distinctions from General Gemma 3
| Aspect | General Gemma 3 | FunctionGemma |
|---|---|---|
| Training focus | Conversational ability | Function calling reliability |
| Output format | Free-form text | Structured schemas + control tokens |
| Fine-tuning benefit | Modest improvement | 58% → 85% (27-point jump) |
| Primary use case | Q&A, summarization, creative writing | Agentic tasks, API automation, tool control |
| Edge compatibility | Supported, but not optimized | Specifically engineered for edge |
| Tokenization | Standard | 256K vocabulary for JSON efficiency |
Why it matters: FunctionGemma is not a generalist made smaller; it is a specialist designed from scratch for a specific, high-value task. This specialization is what enables production-grade accuracy at 270M parameters.
Technical Specifications
Hardware Requirements & Performance
FunctionGemma runs efficiently on consumer devices without GPU acceleration, making it truly universal:
| Metric | Value | Device Example |
|---|---|---|
| Parameter count | 270M | — |
| Quantized model size (INT8) | 288MB | — |
| Peak memory (RSS) | ~551MB | Pixel 8, iPhone 15 Pro, S25 Ultra |
| Prefill throughput | ~1,700 tokens/sec | Samsung S25 Ultra (CPU) |
| Decode throughput | ~125 tokens/sec | Samsung S25 Ultra (CPU) |
| Time-to-First-Token (TTFT) | 0.3 seconds | Mobile CPU inference |
| Context window | 32K tokens | — |
| Unquantized size (BF16) | ~1GB | High-end device (reference) |
| Minimum RAM requirement | 550MB | CPU-only mode |
Deployment comparison:
- Pixel 8, iPhone 15 Pro, Samsung S25 Ultra: Native support, no GPU required
- Older flagship phones (2020+): Quantized INT4 (~72MB), achievable
- NVIDIA Jetson Nano: Full model support
- Edge servers, laptops: Unrestricted
Why it matters: Users are not forced to upgrade hardware. A 2020-era iPhone 12 or Pixel 5 can run this model, dramatically expanding accessibility and reducing device obsolescence concerns.
Mobile Performance After Quantization-Aware Training (QAT)
When deployed to production (with QAT), the performance profile shifts to prioritize speed and battery efficiency:
| Metric | Value |
|---|---|
| Inference speed | ~50 tokens/sec |
| Accuracy (post-QAT) | ~70% of baseline |
| Model size | 288MB (with optimizations) |
| Typical latency (end-to-end) | <150ms for 10-token output |
This profile is suitable for:
- Voice command processing (entire interaction completes in <500ms)
- Real-time smart home automation
- Gaming and interactive applications
- Continuous on-device agent loops
Why it matters: 50 tokens/sec is slow by cloud standards but fast enough for voice UX. A user says “turn on the lights,” and the response completes within perceived instant time.
Unique Capabilities
1. Unified Action and Chat Interface
FunctionGemma can talk to both machines and humans within the same turn.
Step 1: Parse and execute
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Step 2: Summarize for user
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This dual capability is rare; most function-calling models either:
- Generate functions but cannot explain results (tool-only)
- Explain results but struggle with reliable function generation (chat-first)
FunctionGemma does both seamlessly, improving UX and debuggability.
Why it matters: Users get transparency into what the model is doing. If a function fails, the model can apologize and explain. If it succeeds, it can confirm in natural language.
2. Specialization Through Fine-Tuning
Out of the box, FunctionGemma achieves 58% accuracy on mobile actions. With just 100–1,000 domain-specific examples, accuracy jumps to 85%:
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This 27-percentage-point gain is not typical for LLM fine-tuning. It suggests:
- The base model is intrinsically well-suited to function calling
- The data signal is clean and unambiguous (functions have correct/incorrect calls, not subjective quality)
- Specialization works because FunctionGemma was pre-trained with function-calling structure in mind
Comparison to general Gemma 3:
- General Gemma 3 27B fine-tuned on Mobile Actions: ~70–75% (plateau)
- FunctionGemma 270M fine-tuned on Mobile Actions: 85% with minimal data
The 270M model, when specialized, outperforms a much larger generalist. This is the power of architecture-aligned specialization.
Why it matters: Small data, high accuracy = practical economics. Developers don’t need thousands of examples or weeks of training. A weekend sprint of data collection and fine-tuning can yield production-ready models.
3. Edge-Native Architecture
JSON & Multilingual Tokenization
FunctionGemma uses a 256K vocabulary optimized for JSON, control tokens, and multilingual text. This matters because:
Standard LLM tokenization:
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Requires ~20 tokens with typical 50K vocabulary (inefficient, wasteful context)
FunctionGemma tokenization:
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Requires ~10 tokens with 256K vocabulary (50% context saved)
Over a 32K-token context window, this translates to:
- Shorter sequences → faster processing
- Reduced memory → more room for KV cache
- Lower latency → better UX
Quantization-Aware Training
FunctionGemma ships with official quantized versions trained with QAT. QAT is superior to post-training quantization (PTQ) because:
- PTQ: Train at FP32, quantize afterward (70–75% accuracy for aggressive quantization)
- QAT: Train while simulating quantization (85–90% accuracy at same quantization level)
For mobile, Google provides:
- Full precision (BF16): 288MB, 100% baseline accuracy
- INT4 quantized: ~72MB, 95%+ accuracy
- Mobile optimized: ~288MB, 70% accuracy but 50 tokens/sec
Why it matters: Users can choose their own accuracy-vs.-latency tradeoff. A privacy-conscious app on a laptop might use full precision locally; a smartphone might use INT4 to save battery.
Official Demonstrations
Mobile Actions: System-Level Automation
Google provides a fully open-sourced app and Colab notebook demonstrating FunctionGemma controlling Android system functions:
Supported commands (with zero server communication):
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Each command runs entirely on the device. Contacts, location history, calendar data remain private.
Evaluation: After fine-tuning on the Mobile Actions dataset (publicly available), the model achieves 85% accuracy in selecting the correct function and parameters.
TinyGarden: Multi-Turn Logic in Games
Beyond simple one-shot commands, FunctionGemma handles multi-turn workflows. In the TinyGarden demo:
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All without server contact, all within <1 second.
Why it matters: This proves FunctionGemma can handle conditional logic, loops, and sequences—not just simple command mapping. It opens doors to game AI, workflow automation, and multi-step assistant actions.
Hybrid Architecture: Edge + Cloud
FunctionGemma is not positioned as a replacement for large models; rather, as an intelligent gatekeeper in a tiered system:
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Routing heuristic:
Local (FunctionGemma 270M): Time-sensitive, privacy-critical, defined API surface
- “Turn on lights” → system function call
- “Create reminder” → local calendar API
- “Play music” → local media control
- Latency: ~0.3 seconds
Cloud (Gemma 3 27B, Claude, etc.): Reasoning, cross-domain knowledge, undefined scope
- “Analyze my calendar and suggest free time” → reasoning
- “Which restaurant should I book?” → knowledge + reasoning
- Latency: 1–5 seconds (acceptable for non-urgent)
Cost benefit:
- 50% of requests handled locally → free & private
- 50% of requests routed to cloud → 50% fewer API calls, 50% cost reduction
Why it matters: Organizations don’t have to choose between privacy and capability. They can have both by layering edge and cloud intelligently.
Deployment Ecosystem
Fine-Tuning Support
FunctionGemma integrates with all major ML frameworks:
- Hugging Face Transformers (standard PyTorch/JAX)
- Unsloth (4x faster training on consumer GPUs)
- Keras (TensorFlow stack)
- NVIDIA NeMo (enterprise fine-tuning)
Fine-tuning on consumer hardware:
- NVIDIA RTX 4090: 1,000 examples → 1–2 hours
- NVIDIA RTX 3080: 1,000 examples → 4–6 hours
- Apple MacBook M3 Pro: 1,000 examples → 8–12 hours
- Colab (free tier): Supported with quantization
Deployment Runtimes
| Runtime | Strength | Platform |
|---|---|---|
| LiteRT-LM | Mobile-optimized, official Google support | Android, iOS |
| Ollama | Simple local inference, cross-platform | macOS, Linux, Windows |
| vLLM | High-throughput server inference | Linux servers, Kubernetes |
| Llama.cpp | CPU-efficient, extremely lightweight | Any OS with C++ |
| MLX | Native Apple Silicon support | macOS, iPad OS |
| NVIDIA Jetson | Optimized for edge devices | Jetson Nano, Orin, Thor |
| Vertex AI | Managed Google Cloud service | GCP infrastructure |
Why it matters: Every team has a preferred stack. Kubernetes devotees use vLLM. Apple developers use MLX. Indie developers use Ollama. FunctionGemma fits them all.
Open Licensing
All weights are openly licensed under a responsible commercial use license equivalent to Gemma 3:
- Download and use freely
- Fine-tune on proprietary data
- Deploy commercially
- Modify and redistribute (with attribution)
- Not use for illegal purposes (standard clause)
Downloads available from:
- Hugging Face:
google/functiongemma-270m-it - Kaggle: Gemma collection
- Google Vertex AI: Direct integration
- Ollama:
ollama pull google/functiongemma(coming soon)
Use Cases & When FunctionGemma Fits
Ideal Use Cases
1. Smart Home & IoT Automation
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2. Mobile In-App Assistants
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3. Enterprise Automation (Internal APIs)
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4. Gaming & Interactive Apps
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When FunctionGemma Is Not the Right Fit
- General Q&A / knowledge-heavy tasks: Use Gemma 3 27B or larger models
- Undefined function sets: When you need arbitrary code generation or unpredictable API surfaces, larger models are better
- Zero-shot only: If you cannot afford fine-tuning and need strong zero-shot performance, Gemma 3 larger variants are safer
- Complex reasoning across domains: Use Gemma 3 27B or proprietary models (GPT-4, Claude)
Performance Deep Dive: Fine-Tuning Science
The Mobile Actions Dataset
Google released a public dataset to enable reproducible research and developer fine-tuning:
Dataset composition:
- 8 system functions: flashlight, contacts, email, map, WiFi, calendar, reminders, etc.
- ~1,000 examples: Natural language user requests paired with correct function schemas
- Context variables: Current date, time, user preferences (to test reasoning)
- Evaluation set: Held-out examples to measure generalization
Example entry:
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Accuracy Progression
Zero-shot (no fine-tuning):
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Few-shot (in-context learning):
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Fine-tuned (1,000 examples):
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Comparative models:
- Gemma 3 4B fine-tuned: ~75–80%
- Gemma 3 12B fine-tuned: ~80–85%
- GPT-4 zero-shot: ~90%+
FunctionGemma 270M achieves competitive accuracy while being 150–500× smaller than GPT-4, enabling edge deployment.
Fine-Tuning Recipe
Google provides an open Colab notebook to reproduce results:
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Training time on consumer hardware:
- NVIDIA RTX 4090: ~1 hour for 1,000 examples
- Colab (free T4 GPU): ~3–4 hours
- Apple M3 Pro (MLX): ~6–8 hours
Quantization & Model Optimization
Quantization Trade-Offs
| Quantization | Size | Accuracy | Device Target |
|---|---|---|---|
| BF16 (full precision) | 1.0 GB | 100% | High-end phones, laptops |
| INT8 (dynamic range) | 500 MB | 98–99% | Mid-range phones (Pixel 6+) |
| INT4 (aggressive) | 250 MB | 95%+ | Budget phones, Jetson Nano |
| QAT Mobile (post-train) | 288 MB | 70% | Mobile inference (<50ms latency) |
Practical Deployment Guide
High-end device (iPhone 15 Pro, Pixel 8):
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Mid-range device (iPhone 12, Pixel 6):
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Budget device / Jetson Nano:
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Inference Speed by Backend
| Backend | Device | Model Size | Decode Speed | Latency (10 tokens) |
|---|---|---|---|---|
| LiteRT (CPU) | Pixel 8 | 288 MB | 125 tok/sec | ~80ms |
| Core ML (iOS) | iPhone 15 Pro | 288 MB | 110 tok/sec | ~90ms |
| MLX (M3 Pro) | MacBook | 288 MB | 150 tok/sec | ~70ms |
| QAT Mobile | Pixel 8 | 288 MB | 50 tok/sec | ~200ms |
| vLLM (GPU server) | NVIDIA A100 | — | 1,000+ tok/sec | <10ms |
Why it matters: Even at 50 tokens/sec on mobile, response time remains acceptable for voice-UI interactions (<500ms for a typical 5-token response).
Privacy & Security Architecture
Data Flow Comparison: Cloud vs. Local
Traditional Cloud-Based AI Assistant
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Risks:
- Interception during transmission (despite HTTPS)
- Server breach exposes millions of users’ audio/text
- Third-party data brokers access aggregate data
- Regulatory compliance (GDPR fines up to 4% of revenue)
FunctionGemma Local-Only
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Security guarantees:
- Audio never leaves RAM (optional local storage only if user enables)
- Contacts, calendar, location stay within device OS sandbox
- No remote logging, telemetry, or analytics
- Offline-first = no dependency on cloud services
Hardware-Based Security
Modern smartphones have trusted execution environments (TEEs):
- Apple Secure Enclave (iPhones)
- ARM TrustZone (Android)
- Intel SGX (laptops)
FunctionGemma can run within these enclaves for additional isolation. For example:
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Compliance & Regulatory
FunctionGemma’s architecture is automatically compliant with:
- GDPR (EU): No data processed outside EU; users have full data control
- CCPA (California): Users own their data; no sale or sharing
- HIPAA (US Healthcare): Patient data never leaves facility/device
- PCI-DSS (Finance): Payment data never transmitted to ML servers
- LGPD (Brazil): Automatic consent compliance (no external processing)
Cost impact: Zero regulatory fees, no data processing agreements, no compliance audits.
Why it matters: Especially for regulated industries (healthcare, finance, government), on-device models eliminate entire compliance burdens and associated legal costs.
Economic Analysis: Cost vs. Cloud APIs
Annual Cost Comparison
Assumption: 1 million function calls per month (12 million/year)
Cloud API Approach (e.g., OpenAI Function Calling, Anthropic Claude)
| Item | Cost |
|---|---|
| API calls (1M/month @ $0.02–$0.10 per call) | $240,000–$1,200,000 |
| Error handling & retries (10% additional) | $24,000–$120,000 |
| Cloud infrastructure (redundancy, scaling) | $50,000–$200,000 |
| Compliance & data processing agreements | $10,000–$50,000 |
| Annual total | $324,000–$1,570,000 |
| Cost per call | $0.027–$0.131 |
Local FunctionGemma Approach
| Item | Cost |
|---|---|
| One-time model download & quantization | $0 (free) |
| Fine-tuning (200 examples, 1 GPU hour) | $50–$100 |
| Deployment infrastructure (in-app) | $0 (user’s device) |
| Maintenance & updates (2 hours/month) | $1,000/year |
| Annual total | $1,000–$1,200 |
| Cost per call | $0.0001–$0.0001 |
Break-even analysis:
- Month 1: Cloud = $20,000–$100,000; Local = $50–$100
- Month 6: Cloud = $120,000–$600,000; Local = $300–$600
- Month 12: Cloud = $240,000–$1,200,000; Local = $600–$1,200
Local approach becomes economical in Month 1 and saves 99%+ by Year 2.
Hidden Costs of Cloud
Beyond direct API fees:
- Latency cost: Slower UX → higher churn (study: 100ms delay = 1% revenue loss)
- Privacy breach insurance: $2M–$10M+ for SaaS companies
- Data sovereignty: Cannot serve users in regions with data localization laws
- Debugging & support: More difficult when behavior depends on cloud changes
Revenue Opportunity
By going local, companies can:
- Reduce COGS: Cut deployment costs by 99%
- Expand margins: Pass savings to customers or capture profit
- Enter new markets: Serve countries with strict data localization laws (China, EU, India)
- Differentiate: “100% private AI” as marketing advantage
Example: A 10-person team using 100k function calls/day:
- Cloud: $7,200/month → $86,400/year
- Local: $100/month → $1,200/year
- Savings: $85,200/year → fund 1 additional engineer
Getting Started: Implementation Roadmap
Phase 1: Evaluation (Week 1)
- Download FunctionGemma-270M from Hugging Face
- Run zero-shot evaluation on 10–20 test examples
- Decide: Is 58% accuracy acceptable, or does fine-tuning justify effort?
Phase 2: Fine-Tuning (Week 2–3)
- Collect 200–500 domain-specific examples
- Use Colab notebook from Google (free GPU)
- Or use Unsloth for faster training (4× speedup)
- Fine-tune model (2–6 hours on consumer GPU)
- Evaluate on held-out examples
- Iterate if accuracy < 80%
Phase 3: Deployment (Week 4+)
For mobile:
- Use LiteRT-LM + Google AI Edge Gallery for Android
- Use Core ML Tools + MLX for iOS
- Test on target devices (Pixel 6+, iPhone 12+)
For servers:
- Use vLLM or Ollama for inference
- Deploy to Kubernetes, Docker, or serverless
For edge devices:
- Use Ollama on Raspberry Pi
- Use NVIDIA NeMo on Jetson Nano
- Use C++ runtime (llama.cpp) for maximum efficiency
Phase 4: Optimization (Ongoing)
- Monitor accuracy in production
- Collect user requests that fail; add to training data
- Re-fine-tune every quarter with fresh data
- Monitor battery impact; adjust quantization if needed
Challenges & Limitations
Current Limitations
Zero-shot accuracy is moderate (58%)
- Mitigation: Always plan for fine-tuning if production use
Limited to defined API surfaces
- Cannot handle arbitrary function generation
- Mitigation: Use Gemma 3 27B for open-ended tasks; FunctionGemma for known APIs
Requires domain-specific training data
- Mitigation: Collect 200–500 examples; should take 1–2 weeks
Fine-tuned models are specialized (not general)
- A model fine-tuned for smart home will not work well for games
- Mitigation: Maintain separate models or use transfer learning
Addressing Limitations
| Challenge | Solution |
|---|---|
| Moderate zero-shot accuracy | Build 200–1,000 example dataset; fine-tune |
| Requires defined API surface | Design clear function schemas early |
| Specialized models | Use LoRA fine-tuning for parameter efficiency |
| Integration complexity | Use LiteRT or vLLM; both are well-documented |
Conclusion
FunctionGemma represents a fundamental shift in how on-device AI will work. At 270M parameters, it disproves the myth that powerful agent capabilities require billion-parameter models. Fine-tuning to 85% accuracy demolishes the notion that “small models cannot be reliable.” Instant deployment across LiteRT, Ollama, and vLLM shows that edge AI is no longer a research curiosity but a production-ready reality.
For teams building smart home systems, mobile assistants, gaming experiences, or enterprise automation, FunctionGemma eliminates three obstacles:
- Cloud dependency: No more round-trips to external servers
- Privacy risk: All data stays within the device or facility
- Cost drag: API fees drop from $240K–$1.2M annually to under $1K
The model’s specialization for function calling is not a limitation; it is an advantage. By being excellent at a specific task rather than mediocre at everything, FunctionGemma enables developers to build faster, cheaper, and more private applications.
The era of cloud-first AI is ending. The era of edge-native, private, fast, autonomous agents is beginning. FunctionGemma is the first mainstream production-ready tool for building that future.
Summary
- What: Google’s 270M parameter Gemma 3 variant specialized for function calling (agentic tasks)
- Why it matters: 100% local execution → privacy, speed, cost savings; 85% accuracy after fine-tuning → production-ready
- Where to use: Smart home, mobile assistants, gaming, enterprise automation with defined API surfaces
- How to get started: Download from HF, fine-tune with 200–500 examples, deploy via LiteRT/Ollama
- Economics: Replaces $240K–$1.2M/year cloud APIs with <$1K/year local inference
- Status: Fully open-source, commercially licensed, available December 2025
Recommended Hashtags
#FunctionGemma #EdgeAI #OnDeviceLLM #FunctionCalling #PrivacyFirst #LocalAI #GoogleGemma #AIAgents #SmartHome #EdgeComputing
References
- (FunctionGemma: New Gemma model for function calling, 2025-12-17)[https://blog.google/technology/developers/functiongemma/]
- (FunctionGemma model overview, 2025-12-17)[https://ai.google.dev/gemma/docs/functiongemma]
- (Function calling with Gemma, 2025-12-17)[https://ai.google.dev/gemma/docs/capabilities/function-calling]
- (Fine-tune FunctionGemma for Mobile Actions, 2025-12-17)[https://ai.google.dev/gemma/docs/mobile-actions]
- (FunctionGemma Elevates Edge AI Function Calling, 2025-12-17)[https://startuphub.ai/ai-news/ai-research/2025/functiongemma-elevates-edge-ai-function-calling/]
- (google/functiongemma-270m-it, 2025-12-17)[https://huggingface.co/google/functiongemma-270m-it]
- (FunctionGemma: How to Run & Fine-tune, 2025-12-18)[https://docs.unsloth.ai/models/functiongemma]
- (Gemma 3: Google’s new open model, 2025-03-11)[https://blog.google/technology/developers/gemma-3/]
- (Gemma 3: Google’s multimodal model, 2025-10-12)[https://huggingface.co/blog/gemma3]
- (Mobile Model Quantization (2025), 2025-09-17)[https://eonsr.com/en/quantizing-models-for-mobile-inference/]
- (How does edge AI support data privacy?, 2025-11-16)[https://milvus.io/ai-quick-reference/how-does-edge-ai-support-data-privacy-and-security]
- (Mobile AI and Privacy Protection, 2025-12-10)[https://zetic.ai/blog/mobile-ai-and-privacy-protection-the-importance-of-on-device-processing]
- (Edge AI Security & Privacy, 2024-12-16)[https://edge-ai-tech.eu/edge-ai-security-privacy-protecting-data-where-it-matters-most/]
- (LiteRT for Mobile Apps, 2025-10-23)[https://bitcot.com/litert-on-device-ai-for-mobile-apps/]
- (On-device small language models with RAG, 2025-05-19)[https://developers.googleblog.com/google-ai-edge-small-language-models-multimodality-rag-function-calling/]
Updated: 2025-12-19 (KST)