NNavShelf

NavShelf · Free online tools

Small tools that just work.

Fast, privacy-friendly utilities for developers and everyday use. Every tool runs entirely in your browser — nothing is uploaded to a server.

Base64 Encoder / Decoder

Convert text to Base64 and back, with UTF-8 support.

URL Encoder / Decoder

Percent-encode query parameters and decode %XX sequences.

JSON Formatter

Format, validate and minify JSON.

Unix Timestamp Converter

Convert epoch timestamps to readable dates.

Asset Growth Calculator

Project savings and compound returns year by year.

Loan & Mortgage Calculator

Monthly payment, total interest and amortization schedule.

Savings Goal Calculator

How much to save each month, or how long it will take.

AI Number Checker

Flag the numbers in an AI answer that cannot be traced to your source data.

Agent Guardrails Generator

Generate an AGENTS.md rules file, permission allow/deny lists and a review checklist.

AI Token Cost Calculator

Turn a usage log or a workload into a monthly bill, with editable rates and model comparison.

Reconciliation Diff Checker

Compare two lists or CSV exports and find missing, extra and mismatched rows.

License & Renewal Ledger

Turn a license list into annual cost, seat waste and a renewal calendar.

MD5 Hash Generator

Generate an MD5 checksum from text or a file.

Image Compressor

Shrink JPG, PNG and WebP images with a quality slider.

Markdown Preview Editor

Write Markdown and preview the rendered result.

Color Converter HEX / RGB / HSL

Convert between HEX, RGB and HSL with contrast check.

Regex Tester

Highlight every match and capture group of a pattern.

QR Code Generator

Turn a link or text into a downloadable QR code.

Text Diff Checker

Compare two texts line by line and copy a unified diff.

AI Crawler Log Analyzer

See GPTBot and ClaudeBot traffic in your access log.

AI Crawler robots.txt Generator

Write robots.txt rules for AI crawlers.

llms.txt Generator

Build an llms.txt file for AI crawlers.

Keyword Cannibalization Checker

Find queries where your own pages compete.

SEO Head Audit

Check title, canonical, hreflang and schema of a page.

hreflang Validator

Validate hreflang codes and return links.

SEO Agency Vetting Checklist

Questions and red flags before you hire.

NavShelf

A file-manager style bookmark manager. Data stays in your browser.

Why these tools

Most online utilities make you wait for ads, upload your data, or create an account. These tools are plain HTML and JavaScript: they load instantly, work offline, and never send your input anywhere.

Same for the blog: practical guides on organizing bookmarks and getting more out of your browser.