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Password Protected File Detector

Upload any file to instantly check if it is password-protected or encrypted. Our Password Protected File Detector scans file headers and internal structures to detect encryption across PDFs (checking for /Encrypt dictionaries with AES-256, AES-128, and RC4 variants), Office documents (inspecting DOCX/XLSX/PPTX for EncryptionInfo XML, Agile/Standard encryption, XOR obfuscation, and write protection), ZIP archives (detecting PKWARE 2.0 traditional encryption and WinZip AES-256 via bit flags), RAR archives (analyzing RAR 1.5 and RAR 5.0 encryption headers), and 7z files (checking for AES-256 method IDs). Each detection reveals the encryption algorithm, key length, and security strength classification - all without needing the actual password. Everything runs entirely in your browser with nothing uploaded to any server. Free to use, no signup required.

Password Protected File Detector

Upload any file to instantly check if it is password-protected or encrypted. Detects encryption on PDFs (/Encrypt flag, AES-256 vs RC4), Office documents (DOCX/XLSX/PPTX with EncryptionInfo), ZIP archives (PKWARE encrypted), and RAR archives. Shows the encryption algorithm, key strength, and security rating - all processed locally in your browser.

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Supports PDFs, Office documents, ZIP/RAR/7z archives - up to 100 MB

How Encryption Detection Works

This tool analyzes file headers and structure to detect encryption without needing the password. PDFs are checked for /Encrypt dictionaries. Office documents are inspected for EncryptionInfo XML inside their ZIP structure. Archives are checked for encryption flags in their binary headers. All processing runs locally in your browser - no data is uploaded to any server. The tool cannot decrypt files, only detect whether they are encrypted.

Features

Multi-Format Encryption Detection

Detects password protection and encryption across PDF documents (/Encrypt flag, AES-256 vs RC4), Office Open XML files (DOCX/XLSX/PPTX with EncryptionInfo, XOR obfuscation, write protection), ZIP archives (PKWARE 2.0 traditional and WinZip AES-256), RAR archives (RAR 1.5 and RAR 5.0 encryption), and 7z archives (AES-256 header and content encryption).

Encryption Strength Classification

Each detected encryption method is classified by strength: None (no protection), Weak (RC4 40-bit, XOR obfuscation, PKWARE 2.0 traditional), Moderate, Strong (RC4 128-bit, AES-128), and Very Strong (AES-256). Color-coded badges make it easy to assess the security level at a glance.

Detailed Algorithm & Key Information

Beyond just detecting whether a file is encrypted, the tool reveals the encryption algorithm (AES-256, RC4 128-bit, PKWARE), key length in bits, whether the file requires a password, and PDF-specific metadata encryption status. Displays exact PDF version, Office encryption type, and archive encryption flags.

100% Private & Local Processing

All encryption detection runs entirely in your browser. Files are read locally using the File API and JSZip library - never uploaded to any server. PDF headers are scanned for /Encrypt dictionaries, Office ZIP structures are inspected for EncryptionInfo XML, and archive binary headers are analyzed for encryption flags. Complete privacy guaranteed.

Use Cases

Security Auditing

Quickly verify whether sensitive documents in your organization are properly encrypted before distribution. Check that PDF contracts, financial spreadsheets, and confidential reports are password-protected with strong encryption before sharing externally.

Digital Forensics

In forensic investigations, determine if evidence files are encrypted and assess the type and strength of encryption used. Helps investigators plan decryption strategies and estimate effort required for password recovery or brute-force attacks.

Enterprise Compliance

Ensure compliance with data protection policies by auditing documents for encryption. Verify that sensitive files leaving the organization meet minimum encryption standards (AES-256 for PDFs, strong Office document protection) as required by GDPR, HIPAA, and SOC 2 regulations.

IT Support & Administration

Help end-users determine why they cannot open or edit a file by identifying whether it is password-protected or encrypted. Quickly distinguish between corrupted files and protected files without needing the actual password.

Data Recovery Planning

Before attempting file recovery, determine if the target files are encrypted. Encrypted files require different recovery approaches - knowing the algorithm and key strength helps recovery specialists choose the right strategy and estimate success rates.

Cybersecurity Education

Demonstrate how different file formats implement encryption by comparing PDF /Encrypt dictionaries, Office EncryptionInfo XML, and archive encryption headers. Ideal for teaching students about real-world encryption implementations and their security strengths and weaknesses.

About

What Is File Encryption Detection?

File encryption detection is the process of examining a file's binary structure and metadata to determine whether it is password-protected or encrypted - without needing the actual password. Different file formats store encryption information in different ways: PDFs use /Encrypt dictionaries in their header, Office documents embed EncryptionInfo XML within their ZIP structure, and archives use specific bit flags and header types to indicate encryption.

How Does PDF Encryption Detection Work?

PDF files store encryption parameters in an /Encrypt dictionary within the document's cross-reference table and trailer. The tool scans the PDF header for /Encrypt markers, parses the /R (revision) value to determine the encryption standard (RC4 40-bit, RC4 128-bit, AES-128, or AES-256), extracts the /Length parameter for key size, and checks /EncryptMetadata to determine if metadata fields are also encrypted. PDF versions from 1.1 through 2.0 are supported.

How Are Office Documents Checked?

Office Open XML files (DOCX, XLSX, PPTX) are ZIP archives containing XML files. The tool uses JSZip to read the ZIP structure and looks for EncryptionInfo files that contain ECMA-376 XML encryption descriptors. It can detect Agile (AES-128/256), Standard (CryptoAPI RC4), XOR obfuscation (legacy weak), and write/review protection. If JSZip fails to parse the ZIP at all, that often indicates strong ZIP-based password protection on the entire archive.

What About Archive File Encryption?

ZIP archives are checked by scanning for encryption flags (bit 0 of the general purpose bit flag) and strong encryption markers (bit 6) in each local file header. RAR archives are analyzed by parsing the main header flags and scanning for ENC_HEADER types - supporting both RAR 1.5 (AES-128) and RAR 5.0 (AES-256). 7z files are checked for AES-256 method IDs in the start header area and kEncodedHeader properties. All analysis is done on the binary structure without needing the password.

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FAQ
What file formats does this tool support?
The Password Protected File Detector supports: PDF documents (all versions from PDF 1.1 to 2.0), Office Open XML files (DOCX, XLSX, PPTX), ZIP and ZIPX archives, RAR archives (both RAR 1.5 and RAR 5.0 formats), and 7z archives. Other formats are detected by their magic bytes and generic analysis is attempted.
Can this tool decrypt password-protected files?
No. This tool detects whether a file is encrypted or password-protected by analyzing its structure and headers - it does not decrypt, crack, or bypass passwords. It tells you the encryption algorithm, key strength, and protection type so you know what you are dealing with, but you still need the actual password to open the file.
How accurate is the encryption detection?
The detection is highly accurate for standard encryption methods. PDF /Encrypt dictionaries are reliably detected across all PDF versions. Office EncryptionInfo detection works for all ECMA-376 standard encryption (used by Office 2007+). Archive encryption flags are checked at the binary level. The tool also handles fallback scenarios gracefully - if a ZIP file cannot be parsed by JSZip, it correctly assumes strong encryption is present.
What does the encryption strength classification mean?
Strength is classified as: None (no protection detected), Weak (RC4 40-bit, XOR obfuscation, PKWARE 2.0 traditional - these are crackable in minutes), Moderate, Strong (RC4 128-bit, AES-128 - requires significant resources to crack), and Very Strong (AES-256 - considered computationally infeasible to crack with current technology). Color-coded badges (green, red, amber, blue, purple) provide quick visual reference.
Does this tool work with encrypted ZIP files that have password-protected central directories?
Yes. If JSZip cannot parse the ZIP structure at all (which happens with strongly encrypted ZIPs that have encrypted central directories), the tool reports this as Very Strong encryption with AES-256. This defensive detection ensures encrypted files are never mistakenly reported as unencrypted.
Can this tool detect write protection or review-only passwords?
For Office documents, the tool checks word/settings.xml, xl/workbook.xml, and ppt/presentation.xml for writeProtection and documentProtection markers. These are weaker forms of protection that restrict editing but not viewing. They are reported with a "Weak" strength classification since the document can still be opened and read without a password.
Are my files uploaded to any server?
No - absolutely not. All encryption detection runs entirely in your browser using the File API and JSZip library. Your files are read locally and never leave your device. No data is uploaded, logged, stored, or transmitted anywhere. This is a 100% client-side tool.
What is the file size limit?
The tool accepts files up to 100 MB. For Office documents and ZIP files, only the first portion of the file (up to 512 KB for Office docs, 1 MB for ZIPs) needs to be read for encryption detection, making the analysis very fast even for large files. PDF and RAR detection only needs the first few kilobytes of headers.
Is this Password Protected File Detector completely free?
Yes - 100% free, forever. No signup, no account, no premium tier, no usage limits. Check as many files as you need. All processing is done locally in your browser with zero server uploads.