About LocalOnly

LocalOnly is a set of 37 developer utilities - JSON formatting, validation, conversion and inspection, plus everyday encoders, decoders and generators - that run entirely inside your browser. There is no account, no upload step and no application backend.

Who builds and operates LocalOnly

LocalOnly is built and operated by SprintOak, an independent software project based in Hyderabad, India. It is designed, written and maintained by RavikiranReddy Balemla, a Senior Software Engineer in Hyderabad with more than four years of professional experience across multiple stacks - backend services and APIs, frontend applications, and the data plumbing in between. You can verify who that is on LinkedIn, or email directly at hello@sprintoak.com.

That background is the reason the site exists in this form. Debugging production issues for a living means routinely holding a request body that contains a live bearer token, or a log line carrying a customer's details. The first version of these tools was written because reaching for a random online JSON formatter with that payload in the clipboard is a bad habit, and the only reliable way to break a habit is to have something better within reach.

This is one engineer and a toolkit rather than a company, which is worth knowing when you decide how much to trust it. There is no team behind the “we” on this site - it is a habit of writing, not a claim about headcount.

Because SprintOak is the operating entity, email from us arrives from a @sprintoak.com address rather than @localonly.dev. That is expected, not a phishing attempt. The Contact page lists which address to use for which kind of request.

The problem it was built to solve

Most online developer tools are a form that posts your input to a server, runs the transformation there and returns the result. Nothing in the interface tells you this is happening, and for most content it does not matter.

It matters for the content developers actually debug. The request body that is failing contains a bearer token. The log line you are formatting contains a customer's email address. The JWT you are decoding to check an expiry claim belongs to a live session. Once that has been sent to a third party, you have no way to know whether it was logged, cached, retained for abuse prevention, or stored indefinitely - and in a regulated environment you may have created a disclosure you now have to report.

The tasks themselves do not need a server. Parsing JSON, diffing two objects, computing a SHA-256 digest and decoding Base64 are all native browser capabilities. If the work can happen locally, sending the data anywhere is an unnecessary risk. That single observation is the whole premise of the site.

How the browser-only architecture works

LocalOnly is a static export - HTML, CSS and JavaScript files served from a CDN. There is no API route, no database and no server-side processing. This is a stronger guarantee than a privacy promise, because it is structural: there is no endpoint that could receive your payload even if we wanted one.

Transformations run in your browser tab. Heavy work - parsing multi-megabyte documents, diffing large trees, hashing files - is moved onto Web Workers so the interface stays responsive, and output is rendered through virtualized lists so large structures remain scrollable. Since nothing is uploaded, there is no file-size limit imposed by an endpoint; the practical ceiling is your tab's available memory.

A service worker caches the application after your first visit, so every tool keeps working with no connection at all. You can install LocalOnlyas a standalone app from your browser's address bar and use it on a plane or inside an air-gapped network.

What we are careful not to claim

Plenty of sites advertise “we collect nothing” while loading a full analytics stack. We would rather be precise about the difference between two things that often get blurred together.

• The content you process- the JSON, tokens, files and text you paste into a tool - is never transmitted, never logged and never stored. It exists only in your tab's memory and is gone when you close it.
• The site itself loads Google Analytics and Google-served advertising. Those third parties set their own cookies and receive ordinary request information such as your IP address, user agent and which page you opened. That is how the tools stay free.

Both are described in full in the Privacy Policy and Cookie Policy, including how to opt out of personalised advertising and analytics.

Who it is for

The tools are aimed at people who handle other people's data as part of their job: backend and frontend engineers debugging API payloads, SREs reading production logs, QA engineers building fixtures, data engineers moving between JSON, CSV, YAML and XML, and security engineers inspecting tokens. If you work somewhere with a policy against pasting customer data into third-party websites, a browser-only tool is often the only compliant option available to you.

Why the pages are long

A tool that silently repairs your input teaches you nothing about why it broke. Each tool page carries a written reference for the format it handles - what the specification actually requires, the mistakes people hit repeatedly, where a conversion loses information, and when you should reach for a different tool instead. Longer treatments live in the guides.

We also try to state limits honestly. Every tool page has a Limitations section describing what that tool deliberately does not do, because knowing where a tool stops is more useful than a feature list that implies it never does.

Accessibility and security

LocalOnly targets WCAG-AA: full keyboard navigation, a command palette, sensible focus order, semantic markup and screen-reader labels. Details and known gaps are on the Accessibility page. A browser-only architecture also removes whole categories of risk - there is no database to breach and no server log holding your input - and the deployed site ships strict security headers and a tight content security policy, as described on the Security page.

Where it is going

LocalOnly started with JSON and is growing into a broader privacy-first toolbox: more converters, more encoders, local-only sharing links and wider language support. The Roadmap has the current plan. If a tool you need is missing, or one behaves in a way you did not expect, please tell us- most of what has been built so far started as somebody's complaint.