Blog
Practical guides on getting things done with your files — PDFs, images, tokens, data — without ever uploading them to someone else's server.
How to verify a JWT signature
Decoding a JWT proves nothing — verifying the signature is what makes it trustworthy. How HS256 and RS256 verification actually work, and how to check a token without handing it to a third-party server.
· 8 min read
Convert curl commands to axios (and back)
How curl flags map onto axios and fetch options — headers, JSON bodies, form data, auth, query strings — plus the traps that silently change what your request sends.
· 8 min read
Is this JWT still valid?
A valid signature does not mean a valid token. What exp, nbf, and iat actually mean, why clock skew breaks logins, and which claims you must check before trusting a request.
· 7 min read
The Base64 alphabet
The full 64-character table, why the padding character is not part of it, how the URL-safe variant differs, and how to tell standard Base64 from base64url at a glance.
· 7 min read
How to pretty print SQL
Turn a one-line query dumped by an ORM into something readable — indentation, keyword casing, and dialect differences, done locally so production SQL never leaves your machine.
· 6 min read
JWT signing algorithms compared
Symmetric versus asymmetric signing, which algorithm to pick for which architecture, and why the alg header is the most security-critical field in the whole token.
· 8 min read
Which random ID should you use?
Four ways to generate a random identifier, compared on sortability, database index behaviour, length, and collision risk — with a straight recommendation for each case.
· 8 min read
How to make a QR code that never expires
Most free QR generators encode their own tracking link, not yours — so the code dies when they do. Here's the difference between static and dynamic codes, and how to make a permanent one offline.
· 6 min read
How to verify a file checksum
Check that a download arrived intact and untampered by comparing its SHA-256 hash. What a matching checksum proves, what it doesn't, and how to check one without uploading the file.
· 6 min read
How to merge PDF files without uploading them
Combine PDFs entirely in your browser — no upload, no server, no sign-up. Here's why local merging is safer for contracts and IDs, and how to do it in three steps.
· 4 min read
How to compress a PDF without losing quality
Shrink a PDF for email or upload limits while keeping text sharp and selectable — all in your browser, with nothing sent to a server. A practical, private guide.
· 5 min read
What is a JWT, and how do you decode one safely?
A plain-English guide to JSON Web Tokens: what the three parts mean, how signature verification works, and why you should never paste a token into a random website.
· 8 min read
How to convert HEIC to JPG on any device
iPhone photos are HEIC, and half the web can't open them. Here's how HEIC works, when to convert to JPG, and how to do it in your browser without uploading a single photo.
· 5 min read
How to sign a PDF electronically for free
Draw or place your signature on a PDF and download it — no account, no watermark, and no uploading the document to a signing service. Here's how, and whether it's legally valid.
· 5 min read
How to password-protect a PDF
Add a password so only the right people can open a PDF — encrypted on your own device, never uploaded. What real PDF encryption does, its limits, and how to do it in three steps.
· 5 min read
How to extract text from a scanned PDF with OCR
A scanned PDF is just pictures of text — you can't select or search it. Here's how OCR turns those scans back into real, copyable text, entirely in your browser.
· 6 min read
What is Base64 encoding, and when should you use it?
Base64 turns binary data into plain text so it survives systems built for text. Learn what it is, why it makes data ~33% bigger, when to use it, and why it is not encryption.
· 5 min read
A private, offline alternative to online PDF tools
Online PDF tools like iLovePDF and Smallpdf are cloud services — you upload your files to their servers. Here's a private alternative that runs entirely in your browser, so nothing is uploaded.
· 6 min read
How to split a PDF into separate files
Extract a page, pull out a range, or break a big PDF into individual files — entirely in your browser, with nothing uploaded to a server. A quick, private, step-by-step guide.
· 4 min read
How to generate a strong password
What actually makes a password hard to crack, why length matters more than special characters, and how to generate one securely in your browser — never sent over the network.
· 5 min read