FmtDev
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LLM Prompt Sanitizer (PII Remover)

FmtDev LLM Prompt Sanitizer is a free, browser-based tool that safely redact API keys, emails, JWTs, and IPs from your code or logs before pasting them into LLMs. 100% local processing. It runs entirely on your device with zero data transmission, making it safe for proprietary code and sensitive content.

🛡️ 100% Client-Side. Your data never leaves your browser.
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0 Secrets Redacted

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Prompt Privacy in the Era of GPT-5.4: A Complete Security Guide

The Invisible Risk: Why 'Delete Conversation' Isn't Enough

In 2026, AI models are no longer just chatbots; they are agents with memory. When you paste a server log containing an API key or a customer email into Claude 4.6 or GPT-5.4, that data is processed through third-party GPU clusters. Even if you delete the chat, the data has already transited the network. For developers in regulated industries (FinTech, HealthTech), a single 'unmasked' prompt can lead to a massive compliance failure. The only zero-risk solution is redacting sensitive data locally before it ever leaves your machine.

Local-First Sanitization: Building a Human-in-the-Loop Firewall

Effective prompt engineering in 2026 requires a 'Clean Room' approach. By using FmtDev's Prompt Sanitizer, you implement a local firewall. Our tool uses browser-native Regex engines to identify and replace PII (Personally Identifiable Information), JWTs, and secret keys with generic placeholders. This allows the LLM to still understand the structure of your code or logs without ever seeing the actual secrets. It is the gold standard for maintaining 'Data Sovereignty' while leveraging the power of frontier AI models.

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How to use

How to use Prompt Sanitizer

  1. 1

    Paste your raw prompt, logs, or code in the input area.

  2. 2

    The tool instantly identifies sensitive patterns like emails and API keys.

  3. 3

    Choose between Label, Shape, or Length preservation modes.

  4. 4

    Copy the redacted version for safe use in AI models.

FAQ

What data is redacted?
We detect emails, IPv4 addresses, JWTs, and common API key patterns (OpenAI, AWS, etc.).
Is the redaction 100% accurate?
It uses regex-based heuristics which are very effective, but always manually review output for critical data.

Prompt Privacy in the Era of GPT-5.4: A Complete Security Guide

The Invisible Risk: Why 'Delete Conversation' Isn't Enough

In 2026, AI models are no longer just chatbots; they are agents with memory. When you paste a server log containing an API key or a customer email into Claude 4.6 or GPT-5.4, that data is processed through third-party GPU clusters. Even if you delete the chat, the data has already transited the network. For developers in regulated industries (FinTech, HealthTech), a single 'unmasked' prompt can lead to a massive compliance failure. The only zero-risk solution is redacting sensitive data locally before it ever leaves your machine.

Local-First Sanitization: Building a Human-in-the-Loop Firewall

Effective prompt engineering in 2026 requires a 'Clean Room' approach. By using FmtDev's Prompt Sanitizer, you implement a local firewall. Our tool uses browser-native Regex engines to identify and replace PII (Personally Identifiable Information), JWTs, and secret keys with generic placeholders. This allows the LLM to still understand the structure of your code or logs without ever seeing the actual secrets. It is the gold standard for maintaining 'Data Sovereignty' while leveraging the power of frontier AI models.

Watch: Why Prompt Privacy Matters

You Are Leaking Company Secrets Every Time You Use ChatGPT