Software Alternatives, Accelerators & Startups

HackThisSite VS KeptPDF

Compare HackThisSite VS KeptPDF and see what are their differences

HackThisSite logo HackThisSite

Hack This Site is a legal free training ground for users to test and expand their hacking skills.

KeptPDF logo KeptPDF

Redact, edit, OCR, and sign PDFs entirely in your browser. The file never leaves your device. Free, no account needed.
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  • HackThisSite Landing page
    Landing page //
    2021-11-14
  • KeptPDF Landing page
    Landing page //
    2026-08-22

KeptPDF is a PDF toolkit that runs entirely in your browser. Nothing uploads: every tool runs on your own device, so the document never touches a server.

What it does:

  • Redaction that auto-detects names, SSNs, phone numbers, addresses, and dates, then removes the underlying text instead of drawing a box over it. Every redacted file gets an audit certificate that anyone can verify.
  • OCR that makes scanned PDFs searchable, with on-device processing.
  • Sign, annotate, compare, organize, split, merge, compress, convert, watermark, Bates numbering, exhibit stamps, and more. About 25 tools in total.
  • A command line version runs the same redaction engine on your own servers for bulk work: scanning bureaus, litigation support teams, and records departments process thousands of PDFs in one pass.

Who it is for: law firms, accounting practices, clinics, and anyone who shares documents they cannot afford to leak.

The core tools are free with no sign-up. Works offline as an installable app.

KeptPDF

$ Details
freemium $29 / Monthly (Pro, 1 user)
Release Date
2026 May
Startup details
Country
United States
State
Tennessee
Founder(s)
John Whitworth

HackThisSite features and specs

  • Educational Experience
    HackThisSite offers practical, hands-on hacking challenges that help users improve and apply their cybersecurity skills in a controlled, legal environment.
  • Community Support
    The platform has a thriving community of cybersecurity enthusiasts and experts who actively engage in forums and discussions, providing support and knowledge-sharing opportunities.
  • Variety of Challenges
    HackThisSite provides a wide range of challenges, from basic to advanced levels, covering various aspects of cybersecurity, which caters to different skill levels and interests.
  • Legal and Safe Environment
    The site allows users to practice hacking legally, reducing the temptation to engage in unethical hacking activities.

Possible disadvantages of HackThisSite

  • Potential for Misuse
    Despite its educational intentions, there is a risk that some individuals may use the skills learned for unethical or illegal hacking activities.
  • Limited Real-World Scenarios
    While HackThisSite provides valuable practice, some challenges may not fully replicate real-world cybersecurity scenarios, which can limit practical application.
  • Resource Intensity
    Some users may find the challenges resource-intensive in terms of time and effort required to solve them, especially for beginners.
  • Potential Outdated Content
    Certain challenges and content on the site may become outdated as cybersecurity threats and technologies evolve over time.

KeptPDF features and specs

  • Simple PDF Editing
    KeptPDF offers straightforward tools for editing, merging, splitting, and converting PDF files, making it accessible for users who need quick document management without a steep learning curve.
  • Web-Based Accessibility
    Being a web-based tool, KeptPDF can be accessed from any device with an internet connection, eliminating the need for software installation and allowing use across different operating systems.
  • Multiple File Format Support
    The platform supports conversion between PDF and various other file formats, offering flexibility for users who work with documents in different formats.
  • No Installation Required
    Since it operates in a browser, users can save storage space on their devices and avoid compatibility issues that sometimes arise with desktop software installations.
  • Quick Processing
    KeptPDF is designed to process PDF tasks efficiently, allowing users to complete common document tasks like compression or conversion in a relatively short amount of time.

HackThisSite videos

HackThisSite Basic Challenge 1

More videos:

  • Tutorial - HackThisSite: Realistic 1 Tutorial - Uncle Arnold's Band Review
  • Review - HackThisSite Realistic Challenge 1

KeptPDF videos

No KeptPDF videos yet. You could help us improve this page by suggesting one.

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Category Popularity

0-100% (relative to HackThisSite and KeptPDF)
Education
100 100%
0% 0
PDF Readers And Editors
0 0%
100% 100
Security & Privacy
80 80%
20% 20
PDF Tools
0 0%
100% 100

Questions & Answers

As answered by people managing HackThisSite and KeptPDF.

What makes your product unique?

KeptPDF's answer:

KeptPDF runs entirely in your browser. Your file, and the text inside it, never leaves your device. Not to an AI, not even to us. You can open your browser's network tab and watch: the document bytes never go out.

Most online PDF tools upload your file to a server first, and some "AI redaction" services quietly send your document text to a third-party model. That is the exact risk people are trying to avoid when they redact something.

KeptPDF also does true redaction. The text is removed from the file, not covered with a black box you can copy out later. Every redaction produces a verification certificate you can share with the file.

Why should a person choose your product over its competitors?

KeptPDF's answer:

Three reasons.

Privacy you can verify, not just a promise. Processing happens locally in the browser, so there is no upload step to trust. We do send anonymous usage counts for quota, and we say so plainly, but never your document.

Real redaction with proof. Removed text is permanently gone, and you get a certificate showing the file was checked for leftover extractable text. Automated detection cannot catch everything, so a final human review is still your job, and the tool says that too.

It works on a phone. Most PDF suites assume a desktop. KeptPDF was built and used on a phone first, so redacting a document while you are standing in a hallway actually works.

How would you describe the primary audience of your product?

KeptPDF's answer:

Anyone who has to hand a document to someone else and needs the sensitive parts gone first.

In practice that is solo attorneys and small law firms, accountants and tax preparers, healthcare and records staff handling requests, HR teams, and individuals dealing with their own medical, legal, or financial paperwork.

The common thread is not an industry. It is a person who cannot upload a confidential file to a random website, and who does not have an enterprise IT budget to solve it.

What's the story behind your product?

KeptPDF's answer:

A family member got seriously ill. We spent most days at the hospital, and straight answers were hard to come by, so we leaned on AI tools to make sense of the records, notes, and lab results.

But you cannot paste a medical record into an AI chat. You have to strip the names, the ID numbers, the diagnoses first. And almost every tool we found either wanted to upload the whole file to a server, or "auto-redacted" by sending the document text to an online AI. That was the exact thing we were trying to avoid.

Most of this was happening on a phone, at a bedside. So I built the tool I needed: redaction that runs on the device, works on mobile, and never sends the file anywhere. That turned into KeptPDF, which is now a full PDF suite with over 20 tools, all local-first.

Which are the primary technologies used for building your product?

KeptPDF's answer:

The app is plain JavaScript with no front-end framework, which keeps it fast and keeps the code auditable.

PDF work happens in the browser using pdf.js for rendering and pdf-lib for writing. Text recognition uses Tesseract running as WebAssembly. Password and encryption handling uses a WebAssembly build of qpdf. It is a Progressive Web App, so it installs and works offline.

The thin server side is Node on Vercel, with Postgres for accounts, Stripe for billing, and Resend for email. None of those ever see a document.

Who are some of the biggest customers of your product?

KeptPDF's answer:

KeptPDF is early and independent, and we do not publish customer names. The product is privacy-first by design: we never see your documents, and we do not track who our users are or what they work on. Publishing a client list would sit badly next to that.

The user base today is mostly solo attorneys, small firms, accountants, and individuals handling their own records.

User comments

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What are some alternatives?

When comparing HackThisSite and KeptPDF, you can also consider the following products

Hack The Box - An online platform to test and advance your skills in penetration testing and cyber security.

Smallpdf - PDF document management and conversion suite

TryHackMe - TryHackMe is an online platform for learning and teaching cyber security, all through your browser.

iLovePDF - Premium online PDF tool set

VulnHub - VulnHub provides materials allowing anyone to gain practical hands-on experience with digital security, computer applications and network administration tasks.

Sejda - Split, merge and other powerful PDF tools.