Portfolio | Jean Pierre Kolb

JPKCom Developer Tools

At jpkc.com/tools/ I provide a comprehensive collection of over 40 free, browser-based developer tools. The tech stack is built on PHP 8.3, Bootstrap 5, jQuery 4, and modern JavaScript. All tools run entirely in the browser — no data is sent to any server. Processing happens exclusively on the client side, ensuring maximum privacy.

Some tools require access to external resources for certain functions (e.g. DNS lookups, SSL certificate checks, SEO analysis). For this purpose, I developed a dedicated proxy — see the proxy section below.

Code and Text

Beautify: Format, beautify, and deobfuscate JavaScript, CSS, and HTML code. Make JSON and JSONP readable.
Cheat Sheets: 202 cheat sheets for CLI tools, package managers, and web development. Search commands and copy with one click.
Coder: Encode and decode HTML entities, URLs, Base64, JSON strings, JWT, and Data URIs.
Compiler: Compile SASS/SCSS to CSS, beautify and minify HTML, JavaScript, and CSS. Split-view editors with upload and download.
Convertor PRO: Convert between HTML/XML, JavaScript/CSS escapes, Unicode, UTF-8, UTF-16, hexadecimal, URI encodings, and data formats (YAML, JSON, TOML, XML).
CSV Editor: Open, edit, and export CSV files online. Spreadsheet editor with automatic delimiter detection.
JSON Editor: Modern JSON editor with tree, table, and code views. Format, validate, repair, and transform JSON data.
Lorem Ipsum: Generate placeholder text in Latin, English, or German. Choose length by paragraphs, words, or characters.
Markdown Editor: Write Markdown with live preview, synchronized scrolling, GitHub Flavored Markdown support, and HTML export.
Playground: Interactive HTML, CSS/SCSS, and JavaScript editor with live preview, Bootstrap/jQuery assets, and save slots.
Regex Debugger: Test and debug regular expressions with real-time matching, flag support, and an integrated cheat sheet.
Source Viewer: Code editor with syntax highlighting for 100+ languages, code beautification, URL loading, and HTML-to-Markdown conversion.
WP Code Generator: Generate WordPress boilerplate code for plugins, themes, blocks, hooks, CPTs, taxonomies, meta fields, and settings pages.
WYSIWYG Editor: Rich text editor based on TinyMCE with HTML5 local storage. Create and edit HTML content visually in the browser.

Design and Graphics

Colors: Color picker and image color scheme generator. Extract color palettes from images.
Fonts: Preview and compare base fonts, Google Fonts, and custom font files in real time with adjustable size and weight.
GeoPattern: Generate beautiful geometric SVG patterns from any text string.
Graphic Editor: HTML5 image editor for cropping, scaling, and format conversion. Export to PNG, JPEG, WebP, and AVIF.
PDF Tools: Create, view, edit, merge, and split PDF files in the browser. Annotate, highlight, draw, and extract text.
Periodic Table (PSE): Interactive periodic table of all 118 elements with category filter, search, and detailed element data.
Placeholder Generator: Generate custom placeholder images with configurable dimensions, colors, and text. Presets for social media and web banners.
Trianglify UI: Generate algorithmically created low-poly triangle background patterns with customizable colors and complexity.

AI and SEO

llms.txt Generator: Generate llms.txt files for websites. The proposed standard helps AI language models understand web content.
Meta Tags Generator: Generate meta tags: Open Graph, Twitter/X Cards, mobile, security, performance, and structured data (JSON-LD) with live preview.
robots.txt and Sitemap: Generate robots.txt (with user-agent rules, AI bot blocking) and sitemap.xml.
SEO and GEO Analyzer: Comprehensive SEO and GEO analysis: HTTP headers, SSL certificates, redirect chains, meta tags, links, images, structured data, accessibility, robots.txt, and AI readiness scoring.

Security and Utilities

Cryptor: AES-256-bit encryption and decryption of text messages. Client-side encryption with password protection.
DNS, SSL, Redirect, and URL: Check DNS records (incl. DKIM), analyze SSL certificates, trace HTTP redirects, parse URLs, and generate SPF records.
Cron Job Helper: Visual cron expression builder with presets and next-run preview. Setup guides for WordPress, TYPO3, Drupal, Laravel, Docker, and DDEV.
Docker/Podman Composer: Convert docker run and podman run commands to Docker Compose YAML and back.
IP Tools: IPv4 and IPv6 utilities: detect your IP, calculate subnets, convert IP formats, generate IPv6 ULA prefixes.
Generator: Generate passwords, salt and security keys, BCrypt/Argon2 hashes, and TOTP one-time passwords with QR code.
Hash Generator: Generate MD5, SHA-1, SHA-256, SHA-384, SHA-512, SHA-3, and RIPEMD-160 hashes with HMAC support.
Info Tools: Display browser information, HTTP headers, IP address, installed plugins, and HTML5/CSS3 capabilities.
Mail Header Analyzer: Parse and visualize email headers (RFC 5322). Trace delivery routes and check SPF/DKIM/DMARC authentication.
PKI Viewer: Inspect X.509 certificates, PKCS#7/P7M, PKCS#12/PFX, CSR, and keys. View details, check validity, and extract P7M content.
SSH Proxy: Generate SSH tunnel, SOCKS proxy, and port forwarding commands. Configurations and guides for Linux, macOS, Windows, BSD, and WSL.
QR Code Generator: Generate QR codes from text, URLs, or other data with configurable size and error correction.
Time Converter: View international time formats and convert Unix timestamps to human-readable dates and vice versa.
UUID Generator: Generate RFC 4122 compliant UUIDs in various formats.

Localproxy — Proxy for JPKCom Developer Tools

Some of the tools listed above require access to external resources, e.g. for DNS lookups, SSL certificate checks, or SEO analysis. Browser security policies (CORS) normally prevent such access. For this purpose, I wrote a lightweight HTTP proxy in pure Go — no external dependencies, single-file architecture (main.go):

github.com/JPKCom/proxy-jpkcom-dev-tools

How it works: The proxy runs as a standalone binary on your machine and binds exclusively to 127.0.0.1. All requests require per-session token authentication via the X-Proxy-Token header. Built-in SSRF protection prevents access to private IP ranges through DNS resolution checks.
Endpoints: /proxy — Forward HTTP/HTTPS requests with streaming body support
/inspect — Return connection metadata as JSON: SSL certificate chains, TLS versions, IP addresses, headers, and millisecond-precision connection profiling (DNS lookup, TCP connect, TLS handshake, TTFB)
/page — Comprehensive page analysis in a single request: follows redirect chains server-side with per-hop metadata (timing, IP, headers), delivers SSL details, body content, and performance timing
/ping and /version — Health checks and version information
Security and configuration: Configurable origin filtering for production use, configurable DNS servers (defaults to Cloudflare and Google), adjustable timeout and response size limits (default: 50 MB). Categorized JSON error responses for different failure types (DNS, TLS, connection, timeout).
Privacy: By running locally on 127.0.0.1, no data leaves your machine through third parties. The proxy acts as a direct intermediary between your browser and the target server — without external cloud services or intermediate servers.
Platforms: Linux, macOS, Windows, and BSD variants
General purpose: Although the proxy was developed for the JPKCom Developer Tools, it is universally usable — wherever you need a local, authenticated HTTP proxy with SSL inspection and connection profiling.

GitHub Repositories

A selection of my open-source projects on GitHub, sorted by category. You can find my full profile at:
github.com/JPKCom

Proxy

proxy-jpkcom-dev-tools: Local HTTP proxy written in Go for browser-based developer tools. Enables DNS lookups, SSL analysis, and page inspection while bypassing CORS restrictions. See details above.

WordPress Plugins — Content and Display

All plugins require PHP 8.3+ and WordPress 6.9+, use strict typing, and are updated via automatic GitHub-based updates with SHA256 checksum verification.

jpkcom-post-filter: Faceted navigation and filtering of posts, pages, and custom post types via WordPress taxonomies. SEO-friendly URLs with filter state in the path, AJAX filtering with history.pushState and no-JS fallback. Four filter layouts (horizontal bar, columns, sidebar, dropdown), three list layouts (cards, rows, minimal). Native Gutenberg blocks, Elementor widgets, and Oxygen Builder elements. Four-tier caching (object cache, transients, APCu, PHP file cache). Full accessibility with aria-live regions and aria-pressed toggles. No dependencies — no ACF, Bootstrap, or jQuery required.
jpkcom-acf-jobs: Job listing and application management plugin for ACF Pro. Three custom post types (jobs, locations, companies) with hierarchical organization. Flexible job types (full-time, part-time, contract, internship). Schema.org JobPosting integration for Google for Jobs. WPML support, template override system, and Bootstrap 5 compatible.
jpkcom-acf-references: Reference gallery plugin for ACF Pro with interactive client-side filtering and animated transitions. Three custom post types (references, locations, customers). Image gallery with lightbox modal and keyboard navigation. Multiple layout options (list, card grid, image overlay). WPML support, prefers-reduced-motion compatible, and Bootstrap 5 compatible.
jpkcom-simple-lang: Lightweight per-post language selection that overrides the sitewide language setting in the frontend. Uses the WordPress core language system, automatically updates the HTML lang attribute, generates hreflang meta tags for SEO. Compatible with Yoast, Rank Math, and Oxygen Builder. Multisite support.
jpkcom-fa-svg-plugin: Shortcode plugin for embedding Font Awesome Pro (v5.15.4) as inline SVG. Supports all icon types (solid, light, regular, duotone, brands), CSS classes, styles, and title/ARIA labels for accessibility. Works in menus, Gutenberg, and via do_shortcode(). Multisite support.
jpkcom-gutenberg-img-alt: Automatically syncs image alt attributes in the Gutenberg block editor with media library metadata. Dynamic updates via regex — ensures alt texts stay current even when changed in the media library after insertion. Promotes SEO and accessibility.

WordPress Plugins — Security

jpkcom-hide-login: Renames the default WordPress login URL (wp-login.php) to a custom slug. Built-in brute force protection with configurable thresholds (max attempts, time window, block duration). IP whitelist with CIDR support, WP-CLI commands, and multisite support. WooCommerce compatible, REST API safe, no core file modifications.
jpkcom-disable-xmlrpc: Globally disables WordPress XML-RPC: empties the method list via filter and blocks direct access to xmlrpc.php with a 403 error. Protects against automated attacks on the XML-RPC interface.
jpkcom-disable-comments: Completely disables WordPress comment functionality site-wide: removes UI elements from admin, menus, admin bar, and dashboard, disables trackbacks, empties comment arrays, and removes REST API comment endpoints.
jpkcom-argon2: Enables the ARGON2ID algorithm for all WordPress password hashes. Replaces the default hashing with the more modern and secure Argon2id algorithm. Multisite support, no configuration needed.

Social Media Profiles

Mastodon: JPKCom@mastodon.social — Fediverse profile
GitHub: JPKCom@GitHub — Open-source projects and code repositories
GitLab: JPKCom@GitLab — Additional code repositories
Drupal: JPKCom@Drupal — Drupal community profile
XING: Business network profile
LinkedIn: International business network profile
Google Business: Google business profile
Gravatar: Global avatar and profile on WordPress/Gravatar

Logos and Graphics

SVG graphics for download.

/img/JPK.svg: 1260 × 1260 · 69 KB · image/svg+xml
/img/JPKCode.svg: 2764 × 996 · 59 KB · image/svg+xml
/img/JPKCom.svg: 410 × 410 · 1.6 KB · image/svg+xml
/JPKCom.svg: 240 × 240 · 8.7 KB · image/svg+xml
/JPKComBE.svg: 1000 × 1000 · 9.5 KB · image/svg+xml
/JPKCom-6.svg: 1024 × 1028 · 4.6 KB · image/svg+xml

Have questions or feedback about any of these projects? Get in touch.