About utilrepo
utilrepo is a single-author site of focused web utilities, written and maintained by curtis, who also runs the schoolofweb.net engineering book and article series. The goal is narrow: collect the small tools developers and curious users actually open browser tabs for — JSON formatters, encoders, regex testers, image and PDF helpers, payroll and date calculators — into one consistent, browser-only place, with an editorial guide next to every tool.
Why this site exists
Most online utility sites fall into one of two traps: tools wrapped in a heavy upload backend that sends your data to a server you cannot see, or tools with no explanation at all, leaving the user to guess what the output means. utilrepo takes a different position. Every tool is implemented as plain JavaScript that runs inside your open browser tab, so inputs never travel anywhere. And every tool ships with a usage paragraph, two or three worked examples, an FAQ of common gotchas, and a short conceptual note. The page is not just a calculator — it is also a small page about the topic the calculator is for.
Browser-only by design
There is no backend that receives your inputs. JSON you format, JWTs you decode, images you resize, PDFs you merge — all of it happens in the same page you have open. There is no upload step, no account, and no server-side log of what you process. The full data policy, including how local storage is used and what third-party services apply, lives on the Privacy page.
What is covered
At the time of this writing utilrepo publishes 64 tools across 11 categories — developer (encoders, formatters, JWT, regex, hashes), text, design, image, PDF, units, calculators (salary, interest, dates), calendar, security and crypto, time, and a small set of party and picker helpers. The blog adds 22 long-form articles that go deeper into the topics the tools touch: for example why your AWS bill spikes, how TOTP codes work, URL slugs, Unicode and collisions, or regex catastrophic backtracking. All content is offered in English, Japanese, and Korean by hand — not by machine translation.
Editorial approach
Both the per-tool guides and the blog posts are written by curtis. No automated translation pipeline runs on published copy: each language is edited line by line. The voice is intentionally calm and technical — short paragraphs, real numbers and concrete examples, no marketing language, no listicle filler. When a tool has a security implication (JWT decoding, hashing, password generation, HMAC), the surrounding text says so explicitly, including what the tool does not do and where the responsibility still sits with the user.
How utilrepo is funded
The site is supported by display advertising and small one-time tips on Ko-fi. Ads, when present, are clearly labeled and visually separated from the tool input area. utilrepo does not run sponsored placements, paid reviews, or affiliate links inside articles or tool pages. Tool selection and editorial direction are not influenced by advertisers.
Who runs utilrepo
utilrepo is built and maintained by a single engineer who goes by curtis. The same operator publishes the schoolofweb.net engineering book and article series — covering modern React, modern Python, Kubernetes, and AWS — so utilrepo benefits from the same editorial pipeline and the same multilingual writing process. Real-name disclosure is intentionally kept off this site, but the operator is reachable by email and has a public publishing history at schoolofweb.net.
Contact
For questions, corrections, takedown requests, or privacy inquiries, email the address below. Mail is read and replied to in English, Japanese, or Korean. Tool-level bug reports and feature requests are also welcome by email.