I Built a Privacy-Friendly Browser Toolkit with 19 Free Utilities

Small utility tasks interrupt my work more often than difficult programming
problems.
I may need to format a JSON response, inspect the claims inside a JWT, convert a
Unix timestamp, generate a QR code, or remove duplicate lines from a list. None
of these tasks deserves a full application, so I usually search for a small
online tool.
That works, but I kept noticing the same problems. Some utility sites are
cluttered, some require an account, and many do not clearly explain what happens
to the data pasted into them.
So I built CodeKitBox:
https://codekitbox.com/
It is a free collection of browser-based utilities. It currently includes 19
tools, requires no account, and processes common text inputs locally whenever
possible.
What is included?
The first version focuses on common conversion, formatting, testing, and
generation tasks:
Base64, URL, and HTML entity encoding and decoding
JWT decoding and Unix timestamp conversion
JSON formatting and minifying
CSV and JSON conversion
URL parsing
UUID, SHA hash, QR code, password, and random number generation
Regex testing, text comparison, case conversion, and text cleanup
Percentage calculation and word counting
Some tools are primarily for developers, while QR codes, passwords, percentage
calculations, and word counting are useful for a broader audience.
Why process data in the browser?
Online utilities are convenient, but it is easy to paste real information into
them without thinking: API responses, configuration fragments, logs, access
tokens, or unpublished text.
CodeKitBox is a static site built with HTML, CSS, and vanilla JavaScript. For
common operations such as formatting JSON, converting Base64, cleaning text, or
generating passwords, the input does not need to be sent to an application
server.
Local processing is not a replacement for good security habits. Users should
still avoid sharing sensitive production tokens or passwords. A JWT decoder,
for example, can reveal the header and payload, but decoding does not verify the
signature or prove that a token is trustworthy.
A tool should explain its limitations
At first, I thought a utility page only needed an input, an output, and a few
buttons. While building the site, I realized that many users also need to know:
when the tool is appropriate;
what it cannot guarantee;
which mistakes are common;
how their input is handled.
I added practical guides for Base64, JWT, JSON, QR codes, and strong passwords.
The corresponding tool pages also include common uses, warnings, privacy notes,
and frequently asked questions.
Some examples:
Base64 is encoding, not encryption.
Decoding a JWT is not signature verification.
Standard JSON does not allow trailing commas or single-quoted strings.
A QR code should be tested at its final printed size.
Password length, randomness, and uniqueness matter more than clever
substitutions.
These are simple points, but they make the tools safer and more useful for
people who are learning.
Implementation
I deliberately avoided a large frontend framework. The website is built with
plain HTML, CSS, and JavaScript and deployed as static assets on Cloudflare.
Tool pages and guides are generated by local scripts so that dedicated English,
Simplified Chinese, and Japanese pages can be maintained consistently. The site
also includes clean URLs, canonical links, hreflang, a sitemap, and structured
data.
The source code is available on GitHub:
https://github.com/ltdragon200806/codekitbox
What I learned
The most time-consuming part was not implementing individual conversions. It
was making the whole collection feel consistent:
keeping controls predictable across tools;
making mobile layouts usable;
writing accurate privacy and security explanations;
creating localized pages without breaking URLs;
avoiding thin pages that contain only an input box.
Building a small product also changed how I think about feature count. Adding
another tool is easy, but improving a useful tool based on real feedback is
usually more valuable.
What comes next?
The site is new, so the next step is to learn which tools people actually use.
Current ideas include:
QR code download and copy actions;
discount, percentage-change, and tip calculator modes;
better JSON error locations;
more practical guides;
continued mobile and accessibility improvements.
I would appreciate feedback:
Which tool is the most useful?
Which page feels confusing or incomplete?
What small utility do you repeatedly search for?
What matters most in an online utility: speed, privacy, functionality, or a
clean interface?
Try CodeKitBox:
https://codekitbox.com/
GitHub:
https://github.com/ltdragon200806/codekitbox