The Ultimate Guide to Free Developer Tools in Your Browser

Every developer accumulates a mental list of go-to sites for quick tasks: decode that Base64 string, validate this JSON blob, check what that JWT actually contains. The problem is that list usually includes a dozen different sites — each with their own cookie banners, sign-up prompts, and privacy questions.

SoftStash consolidates the most essential developer utilities into a single, fast, privacy-first suite. Everything runs locally in your browser. No uploads. No API keys. No rate limits. This guide walks through each tool and shows you exactly when and why you'd reach for it.

JSON Formatter & Validator

JSON is the lingua franca of modern APIs. When you're staring at a minified 3KB blob returned by an endpoint, the JSON Formatter makes it instantly readable.

What it does

• Format & pretty-print: Takes compact JSON and adds indentation and line breaks
• Validate: Flags syntax errors with the exact line and character position
• Minify: Strips all whitespace to produce compact JSON for payloads
• Tree view: Explore nested objects and arrays in a collapsible tree

Common scenarios

Paste an API response from your terminal to understand its structure:

# Raw curl output
curl -s https://api.example.com/user/42

# Minified response that's hard to read:
{"id":42,"name":"Alice","roles":["admin","editor"],"meta":{"created":"2024-01-01","active":true}}

# Paste into SoftStash JSON Formatter → instantly readable:
{
  "id": 42,
  "name": "Alice",
  "roles": ["admin", "editor"],
  "meta": {
    "created": "2024-01-01",
    "active": true
  }
}

Base64 Encoder / Decoder

Base64 encoding appears everywhere: email attachments (MIME), embedding images in CSS, encoding binary data for APIs, and storing credentials in config files. The Base64 tool handles both encoding and decoding with support for standard Base64 and URL-safe Base64 variants.

When you need it

• Decoding a Authorization: Basic ... header to see the username:password
• Encoding an image to embed directly in a CSS url() or HTML src attribute
• Inspecting Base64-encoded configuration values in Kubernetes secrets
• Encoding binary payloads for REST APIs that don't accept raw bytes

# Decoding a Kubernetes secret value
echo "dXNlcjpwYXNzd29yZA==" | base64 -d
# Output: user:password

# Same thing — paste into SoftStash Base64 Decoder, no terminal needed

JWT Decoder

JSON Web Tokens are used for authentication in virtually every modern web application. When something goes wrong with auth — an expired token, a missing claim, an unexpected audience — you need to inspect the token right now, not write a script to do it.

The JWT Decoder accepts a JWT string and immediately displays the decoded header, payload, and signature verification status. It highlights the expiry time (exp claim), issued-at time (iat), and tells you whether the token is currently valid, expired, or not-yet-valid.

// A typical JWT has three Base64-encoded parts separated by dots:
// eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c2VyXzQyIiwiZXhwIjoxNzA5MDAwMDAwfQ.sig

// SoftStash JWT Decoder shows:
// Header:  { "alg": "HS256" }
// Payload: { "sub": "user_42", "exp": 1709000000 }
// Status:  ⚠ Expired (expired 3 days ago)

UUID Generator

Universally Unique Identifiers (UUIDs) are essential for database primary keys, idempotency keys, correlation IDs, and distributed system design. The UUID Generator produces cryptographically random v4 UUIDs using crypto.randomUUID() — the browser-native API that produces properly random identifiers, not pseudo-random ones.

Use cases

• Generating test database IDs during development without hitting your database
• Creating idempotency keys for payment API requests
• Bulk-generating UUIDs for seed data or fixture files
• Creating correlation IDs for distributed tracing during debugging

// Generated v4 UUIDs:
550e8400-e29b-41d4-a716-446655440000
f47ac10b-58cc-4372-a567-0e02b2c3d479
6ba7b810-9dad-11d1-80b4-00c04fd430c8

Hash Generator

Cryptographic hashing is used for checksums, password storage (never raw!), content-addressable storage, and data integrity verification. The Hash Generator computes MD5, SHA-1, SHA-256, and SHA-512 hashes using the browser's native crypto.subtle.digest() API — the same underlying implementation your OS uses.

When developers reach for this

• Verifying a downloaded file's checksum against the published hash
• Computing the SHA-256 of an API request body for AWS Signature Version 4
• Generating an ETag value for a static resource
• Creating a content hash for cache-busting in build pipelines
• Checking whether two large text blobs are identical without diffing them character by character

Input: "Hello, SoftStash!"

MD5:    a4e1c5f0e8d2b3c7a1f6e9d4b2c8a0f3
SHA-1:  3f4a7b2e1c9d5f0a8b3e6c4d2a1f7e9b5c0d8a2
SHA-256: 9b2e4f1a7c3d6e0b8f5a2c4d7e1b3f6a9c2e5d0b8f3a6c1e4d7b0f9a2c5e8
SHA-512: 2c4a6e8f0b1d3f5a7c9e1b3d5f7a9c1e3b5d7f9a1c3e5b7d9f1a3c5e7b9d...

Regex Tester

Regular expressions are powerful and notoriously difficult to write correctly under pressure. The Regex Tester gives you a real-time environment: as you type your pattern and test string, matches are highlighted instantly. It supports all JavaScript regex flags (g, i, m, s, u) and shows captured groups in a structured view.

Practical examples

• Validating email addresses, phone numbers, or postal codes for form input sanitization
• Writing log-parsing patterns for structured log extraction
• Testing URL routing patterns before committing them to Express or Next.js config
• Crafting sed/awk-compatible patterns without a terminal

// Pattern to extract IP addresses from log lines:
Pattern: /(?:d{1,3}.){3}d{1,3}/g

Test string:
"Request from 192.168.1.42 at 2024-01-15 — origin: 10.0.0.1"

Matches:  [192.168.1.42]  [10.0.0.1]

URL Encoder / Decoder

URLs can only contain a limited set of ASCII characters. Special characters — spaces, ampersands, equals signs, non-ASCII text — must be percent-encoded. The URL Encoder/Decoder handles both directions and distinguishes between encodeURI (encodes a full URL, preserving structure characters) and encodeURIComponent (encodes a URL parameter value, encoding everything).

Input:   "search query with spaces & symbols=true"
Encoded: search%20query%20with%20spaces%20%26%20symbols%3Dtrue

// Useful when constructing query parameters manually or debugging
// 400/422 errors caused by unencoded special characters in API requests

YAML ↔ JSON Converter

Configuration files often come in YAML (Kubernetes manifests, GitHub Actions workflows, Helm charts, Docker Compose), while APIs and code work with JSON. The YAML ↔ JSON Converter translates between both formats instantly, preserving types, nested structures, and array ordering.

# YAML input (Kubernetes deployment snippet):
spec:
  replicas: 3
  selector:
    matchLabels:
      app: api
  template:
    metadata:
      labels:
        app: api

// JSON output:
{
  "spec": {
    "replicas": 3,
    "selector": { "matchLabels": { "app": "api" } },
    "template": { "metadata": { "labels": { "app": "api" } } }
  }
}

Cron Expression Parser

Cron expressions are concise but cryptic. A single mistake in a cron schedule can mean a job runs every minute instead of once a month. The Cron Parser translates any cron expression into plain English, shows you the next 10 scheduled run times, and validates the expression against standard and extended cron formats.

Expression: 0 2 * * 1
Meaning: At 02:00 AM, every Monday

Expression: */15 9-17 * * 1-5
Meaning: Every 15 minutes between 9 AM and 5 PM, Monday through Friday

Expression: 0 0 1 * *
Meaning: At midnight on the 1st of every month

Number Base Converter

Systems programmers, embedded developers, and anyone working close to hardware regularly need to convert between binary, octal, decimal, and hexadecimal. The Number Base Converter converts between all four bases simultaneously and handles both integer and large number inputs.

Common scenarios

• Converting memory addresses from hex to decimal for comparison
• Understanding bitmask values by seeing them in binary
• Decoding Unix file permissions written in octal (chmod 755 → binary 111 101 101)
• Working with color values: HTML hex #FF6B35 → RGB decimal components
• Debugging protocol byte sequences in networking or embedded firmware

Input: 255

Binary:      11111111
Octal:       377
Decimal:     255
Hexadecimal: FF

// chmod 644:
Octal 644 → Binary: 110 100 100
→ Owner: read+write, Group: read, Others: read

Quick Reference: All Developer Tools at a Glance

Why SoftStash Instead of npm Packages or Cloud APIs?

The honest comparison: when should you use SoftStash vs. installing a package or calling an API?

The answer is: use SoftStash for the manual, exploratory, one-off tasks that would be overkill to script. Decoding a JWT to debug an auth issue, formatting an API response to understand its shape, generating a UUID for a one-time test — these are exactly the moments where a fast, no-friction browser tool saves 10 minutes of setup for a 10-second job.

Beyond Developer Tools: More SoftStash Utilities

SoftStash covers far more than developer utilities. The same privacy-first, no-upload approach applies to:

• Image tools: Image compression, AI background removal, resizing, format conversion
• Text tools: Markdown editor, text diff, case converter, Lorem ipsum generator
• Security tools: Password generator, password strength checker, text encryption
• Productivity: Pomodoro timer, todo list, notepad, world clock

Related tools: JSON Formatter · JWT Decoder · Hash Generator · Regex Tester · Base64 · UUID Generator · Cron Parser · YAML ↔ JSON