How does Defndr block spam without a database?

Defndr uses pattern matching and keyword-based filtering that runs entirely on your device. You can customize rules to match your needs. No external spam database means no data leaves your iPhone.

Defndr – Privacy-First SMS Spam Blocker for iPhone

How It Works

Powerful spam filtering that never leaves your device

Instant Blocking

Spam texts are stopped in real-time before they hit your inbox. Configure once, protected forever.

On-Device Processing

Every message is analyzed locally on your iPhone. Zero cloud uploads, zero compromises.

Custom Rules

Build your own keyword allowlists and blocklists. You decide what gets through.

Open Source

Core filtering logic is public on GitHub. Audit the code yourself—no black boxes.

See It In Action

Clean interface, powerful controls

Defndr iOS spam blocker filtering interface showing real-time SMS blocking

Dashboard & Stats

Custom keyword rules and blocklist management for spam filtering

Custom Filtering Rules

Log of filtered spam messages with detailed blocking reasons

Blocked Messages Log

Privacy By Design

On-device processing isn't a feature. It's a requirement.

Your Messages Never Leave Your iPhone

Cloud-based spam filters upload your texts to remote servers for "analysis." That means verification codes, banking alerts, medical info, personal conversations—all stored on someone else's computer.

Even when they claim data is "anonymized," the metadata alone is revealing: who you talk to, when, how often, and what keywords appear in your messages.

Defndr is different. Pattern matching and filtering happen entirely on your device using rules you control. No servers. No databases. No profiles. Just local processing that respects your privacy.

The Difference Is Clear

Not all spam filters are created equal

Cloud-Based Filters

Messages uploaded to remote servers
Permanent message records stored
Metadata harvested and analyzed
Third-party server access
Requires constant internet connection
Privacy policy full of loopholes

Defndr (Your iPhone)

100% local processing
Zero message storage or uploads
No metadata collection whatsoever
No third-party access ever
Works perfectly offline
Open source & auditable code

Questions

Everything you need to know about Defndr

Does Defndr scan my messages online?

No. All filtering happens locally on your iPhone. Your messages never leave your device. There are no cloud servers involved.

Does it collect any data?

No. Defndr doesn't collect, store, or transmit any data. No analytics, no telemetry, no tracking. We don't even have servers to send data to.

Is it really open source?

Yes. The core filtering logic is publicly available on GitHub. Audit it yourself.

How does it block spam without a cloud database?

Defndr uses pattern matching and keyword-based filtering that runs entirely on your device. You customize the rules. No external database means no data leaves your iPhone.

Does it work offline?

Yes. Since all processing is on-device, Defndr works perfectly in airplane mode or anywhere without internet.

Will it block important messages?

You control the rules. Create custom allowlists to ensure messages from specific senders or with certain keywords always get through. Review blocked messages anytime.

Are there ads or subscriptions?

No ads. Ever. Defndr is free to download with core features available. Unlock advanced filtering with an annual subscription or lifetime purchase.

Take Back Control

Stop spam texts without sacrificing your privacy.

Download Free Visit Defndr.org

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