Curated list · 6 picks

Chrome extensions that work locally in your browser

Extensions built around processing on your device — files, text and numbers stay in the browser. Check each store listing's privacy section for the details.

Latest change to a listed extension: Apr 28, 2026

  1. 1

    Local PDF Toolkit

    Merge, split and secure PDFs on your device.

    Merge, split, and secure PDF files entirely on your device with zero cloud uploads. Your documents stay private and safe since all processing happens locally in your browser.

    PDF, Files & DataFree4.4 out of 5, editor score
    DetailsAdd to Chrome (opens Chrome Web Store)
  2. 2

    DataFormat Pro

    Format data without pasting it into a website.

    Format, validate, and convert structured data instantly with a powerful browser-based tool. Improve readability, detect errors, and manage multiple data formats with a fast and developer-friendly interface.

    PDF, Files & DataFree4.9 out of 5, editor score
    DetailsAdd to Chrome (opens Chrome Web Store)
  3. 3

    DataFlow Converter

    Convert CSV, JSON and TSV in the browser.

    Convert CSV, JSON, and TSV files instantly with advanced filtering, sorting, and formatting. Fast, offline, and privacy-focused tool for efficient data transformation directly in your browser.

    PDF, Files & DataFree4.6 out of 5, editor score
    DetailsAdd to Chrome (opens Chrome Web Store)
  4. 4

    Message Encryptor

    Encrypt text before sharing it.

    Securely encrypt and decrypt messages and files using AES-GCM encryption. Fast, private, and fully offline tool with strong security, designed to protect sensitive data directly in your browser.

    Privacy & SecurityFree4.7 out of 5, editor score
    DetailsAdd to Chrome (opens Chrome Web Store)
  5. 5

    Age Calculator

    A quick calculator with no account needed.

    Calculate your exact age instantly with accurate results in years, months, and days. Simple, fast, and offline tool for quick age calculations directly in your browser.

    Calculators & FinanceFree4.7 out of 5, editor score
    DetailsAdd to Chrome (opens Chrome Web Store)
  6. 6

    Text to PDF

    Turn text into a PDF in the browser.

    Convert any plain text or formatted content into a polished, downloadable PDF instantly. Supports custom formatting options, fonts, and layouts for professional output.

    Writing & TextFree4.7 out of 5, editor score
    DetailsAdd to Chrome (opens Chrome Web Store)

About this list

What is the best local-first Chrome extension?

Our top pick is Local PDF Toolkit: Merge, split and secure PDFs on your device. The rest of the list is ranked by how often our editors reach for each one.

How was this list chosen?

AltFTool editors picked and ordered these from the extensions we publish, based on what each one does and how polished it is. It is not based on paid placement or user review counts.

Are the extensions on this list free?

Yes. Every extension here is free to install from the Chrome Web Store and needs no AltFTool account.

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