© 2026 José Carrillo
Zefer Project
Open-source encryption tool, 100% client-side. Web and CLI under the MIT License.
carrilloapps/zefer
End-to-end encryption for text and files. No servers, no traces, no cookies.
carrilloapps/zefer-cli
The same encryption from your terminal. Files 100% compatible with the web: same binary format, same cryptographic parameters.
About the project
Zefer was born from the need to share sensitive information securely without relying on third-party services. All encryption happens in the user's browser using the Web Crypto API. The .zefer files are completely self-contained: they hold the secret encrypted with AES-256-GCM, encrypted security metadata, and a minimal public header. The project is open source under the MIT license and is designed to be deployed on any static hosting platform.
Key features
AES-256-GCM encryption with PBKDF2-SHA256 key derivation (300k to 1M iterations). Everything happens in your browser.
ZEFER3 format supporting text and any file type (images, ZIPs, PDFs, etc.).
Dual passphrase, reveal key, secret question, IP restriction, expiration, and attempt limit.
Available in Spanish, English, and Portuguese. Light and dark mode with automatic OS detection.
Automatic detection of RAM, CPU, GPU, and platform to dynamically calculate the file limit at 80% of capacity.
Full compliance with GDPR (EU), CCPA (California), LGPD (Brazil), and Law 1581 (Colombia). No cookies, no trackers, no analytics.
The official CLI
zefer-cli brings every Zefer capability to the terminal: file and text encryption and decryption, a 7-mode password generator, security analysis for passwords and .zefer files, and a built-in MCP server for AI agents. Use it three ways: as a CLI (npm or npx), as an MCP server, or import it as a programmatic library (ESM/CommonJS) since v1.3.0. Also available as a standalone binary with no Node.js required.
Full cross-compatibility: a file encrypted on the web decrypts in the CLI and vice versa (ZEFB3/ZEFR3, same parameters).
Web parity: keygen with 7 modes and advanced options, analyze for passwords, and info with deep .zefer file analysis.
Built-in MCP server: exposes encryption, decryption, keygen, analysis, and inspection as tools for AI agents.
Programmatic library (v1.3.0): import zefer-cli in Node.js (ESM or CommonJS) and call encodeZefer, decodeZefer, analyzePassword, and generateWithOptions directly in your code.
Standalone binaries for Linux (x64/ARM64), macOS (Intel/Apple Silicon), and Windows, with SHA-256 checksums. No Node.js.
Quick install
npm install -g zefer-cli
npx zefer-cli keygen
zefer encrypt secret.txt -p "passphrase"
# or import it as a library (ESM / CommonJS)
import { encodeZefer, analyzePassword } from "zefer-cli";Tech stack
| Framework | Next.js 16.2.7 (React 19) |
| Language | TypeScript 6 |
| Styling | Tailwind CSS v4 |
| Encryption | Web Crypto API (AES-256-GCM) |
| Key Derivation | PBKDF2-SHA256 (300k-1M iter.) |
| Compression | CompressionStream API (Gzip/Deflate) |
| Icons | Lucide React |
| Hosting | Vercel / Any static host |
| License | MIT |
Creator
José Carrillo
@carrilloappsSenior fullstack developer and Tech Lead with over 10 years of experience. Specialized in Go, React, NestJS, React Native, and cloud architectures.
Support the project
Zefer is free and open source. If you find it useful, consider making a donation to support the development and maintenance of the project.
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