DEV Community: Stone

Markdown Viewer – A Fast, Privacy-First & Feature-Rich Online Editor

Stone — Fri, 07 Aug 2026 11:49:56 +0000

Finding an online Markdown editor that is fast, privacy-first, fully client-side, and packed with modern features (like LaTeX, Mermaid diagrams, and one-click rich exporting) shouldn't be hard. Yet, many existing tools are either bloated with mandatory sign-ups, lack proper diagram/math rendering, or send your sensitive drafts to remote servers.

That’s why we built Markdown Viewer — a lightweight, zero-setup, fully interactive web application designed specifically for developers, technical writers, and content creators.

In this post, I’d love to walk you through why we built it, its core features, and the tech stack powering it.

Why Another Markdown Editor?

Most technical writers face a few common annoyances with existing tools:

Privacy Concerns: Many web editors upload your text to cloud servers for rendering or draft saving.
Missing Advanced Syntax: Writing technical papers or docs often requires math equations ($\text{LaTeX}$) and architecture diagrams ($\text{Mermaid}$), which aren't always supported smoothly.
Export & Publishing Friction: Converting Markdown into clean HTML with inline CSS for newsletters, WeChat articles, or styled PDFs is often tedious.
Bloated Workflows: Forced logins, heavy ads, or missing multi-tab support slow down quick editing tasks.

We wanted a tool that opens instantly, keeps 100% of data local to your browser, renders everything seamlessly, and lets you export in multiple formats effortlessly.

Key Features at a Glance

1. 100% Client-Side Privacy & Zero Setup

No registration required: Open the site and start typing immediately.
Client-Side Rendering: Powered by marked & CodeMirror 6, all rendering happens strictly inside your browser. Sanitized with DOMPurify to guard against XSS.
Offline & Local Storage: Auto-saves your work in localStorage without cloud tracking.

2. Math & Diagram Powerhouse

LaTeX Math Equations: Full support for inline $E = mc^2$ and block math $$ \int_0^\infty e^{-x^2} dx $$ via KaTeX (lazy-loaded for speed).
Interactive Mermaid Diagrams: Render flowcharts, sequence diagrams, Gantt charts, and state diagrams seamlessly. Includes a dedicated diagram toolbar to copy PNG/SVG or view in fullscreen.
GFM (GitHub Flavored Markdown): Tables, task lists, strikethrough, and auto-links. Checkboxes in the preview pane are interactive and sync back to your source code.

3. 50+ Custom Themes & Social Publishing

Preset Publishing Themes: Choose from over 50+ beautifully curated CSS themes (Classic, Minimal, Dark, Vibrant, MWeb style, and WeChat-optimized layouts).
Inline CSS Juice Engine: Automatically converts CSS rules into inline styles for seamless copy-pasting into newsletter tools or WeChat Official Accounts.

4. Versatile Import & Export Options

Multi-Format Export: Export your documents to Markdown (.md), standalone HTML, styled PDF (print/download), or high-res PNG images.
Long-Image Splitting: Automatically split long articles into fixed-size images for image-based sharing platforms.
Drag & Drop: Easily drop .md files directly into the editor.

5. Developer-Friendly Editor Experience

CodeMirror 6 Engine: Modern, performant editor core with line numbers, code folding, and One Dark / Light modes.
Bidirectional Sync Scrolling: Editor and preview scroll together in perfect percentage sync.
Multi-Tab Workspace: Work on multiple documents simultaneously with tab creation, renaming, and duplication.
Serverless URL Sharing: Share documents instantly without a database! Content is compressed with pako (gzip) and encoded into a clean #share= URL hash.

The Tech Stack

Built with modern web standards and performance in mind:

Framework: Next.js 16 + React 19 + TypeScript
Styling: Tailwind CSS v4 + Responsive CSS Variables
Editor: CodeMirror 6 (@codemirror/lang-markdown)
Parser & Sanitizer: marked + DOMPurify
Math & Visuals: KaTeX + Mermaid + highlight.js (190+ languages)
Compression: pako (zlib/gzip client-side compression)

What’s Next? (Roadmap)

We are actively improving Markdown Viewer based on community feedback. Some features currently on our roadmap include:

Editor Find & Replace (powered by @codemirror/search)
Enhanced Keyboard Shortcuts (Ctrl+1..6 for headings, Ctrl+B for bold)
Footnotes & Callout Alerts (> [!NOTE] / > [!WARNING])
AI Writing Assistant (optional API key integration for summaries & translations)
Local Directory / Workspace Management

Try It Out & Share Your Feedback

Check out the live web app here: markdownviewer.org

We’d love to hear your thoughts:

What Markdown features do you rely on most in your daily workflow?
What themes or exports would make your publishing process easier?

Drop a comment below or join the discussion. Happy writing!

What is Image Metadata?

Stone — Fri, 20 Mar 2026 11:01:33 +0000

Every photo you take carries more than just pixels. Hidden within the file is a rich layer of metadata — data about the data — that records everything from your camera settings and GPS coordinates to copyright information and color profiles.

This guide explains the major image metadata standards, what they contain, why they matter, and how to manage them.

What is Image Metadata?

Image metadata is structured information embedded within an image file that describes its properties, origin, and context. It does not affect what the image looks like, but it provides machine-readable details about how, when, where, and by whom the image was created.

A single photo can contain hundreds of metadata fields spanning multiple standards. These fields are stored in designated segments of the file header — before the actual pixel data begins.

The Three Major Metadata Standards

The image industry relies on three complementary standards. Each serves a different purpose, and a single image file often contains all three simultaneously.

1. EXIF (Exchangeable Image File Format)

What it is: EXIF is the standard that records technical information captured automatically by the camera at the moment of shooting. It was first established in 1995 by the Japan Electronic Industries Development Association (JEIDA), and is now maintained by CIPA and JEITA. The latest version, Exif 3.0, was released in May 2023 with UTF-8 support. (Wikipedia)

What it contains:

Category	Example Fields
Camera info	Make, Model, Lens model, Serial number
Exposure settings	Shutter speed, Aperture (f-stop), ISO, Metering mode
Date & time	DateTimeOriginal, DateTimeDigitized, Timezone offsets
GPS location	Latitude, Longitude, Altitude, Direction
Image properties	Resolution, Orientation, Color space
Flash	Flash fired, Flash mode, Flash energy

Key characteristic: EXIF data is written by the camera hardware and is generally read-only in normal workflows. Modifying it requires specialized tools.

2. IPTC (International Press Telecommunications Council)

What it is: The IPTC standard was developed in 1990 by the International Press Telecommunications Council to standardize the exchange of news content among newspapers and wire services. In 1994, Adobe Systems created a specification for embedding IPTC data directly into digital image files, which became known as "IPTC headers." (Wikipedia)

What it contains:

Category	Example Fields
Description	Headline, Caption/Description, Keywords
Creator	Photographer name, Job title, Contact info
Rights	Copyright notice, Usage terms, License URL
Origin	City, State/Province, Country, Location
Workflow	Instructions, Urgency, Category

Key characteristic: IPTC data is human-authored — it's the editorial layer that tells you what the photo is about and who owns it. It is the most widely used standard among news agencies, photo libraries, and stock photography platforms. (IPTC)

3. XMP (Extensible Metadata Platform)

What it is: XMP was created by Adobe Systems and became an ISO standard (ISO 16684-1) in 2012. It is an XML-based metadata framework with powerful extensibility — it can encapsulate both EXIF and IPTC data, plus custom namespaces for any additional information. (Wikipedia) (Adobe)

What it contains:

Category	Example Fields
Editing history	Software used, Edit steps, Develop settings
Ratings & labels	Star rating (0-5), Color label
Rights management	Marked, WebStatement, UsageTerms
Embedded EXIF/IPTC	Mirrors of EXIF and IPTC fields
Custom schemas	Any vendor or user-defined fields

Key characteristic: XMP is the most flexible standard. Adobe Lightroom, for example, saves all non-destructive editing instructions (white balance, curves, crop) as XMP data — either embedded in the file or in a separate .xmp sidecar file. (Adobe)

How They Work Together

These three standards are complementary, not redundant:

EXIF = What the camera recorded (technical)
IPTC = What the human added (editorial)
XMP = What the software tracked (processing + everything else)

A professional photo workflow typically starts with EXIF from the camera, adds IPTC in a DAM (Digital Asset Management) tool, and accumulates XMP through post-processing in Lightroom or Photoshop.

ICC Profiles: The Color Metadata

Is an ICC profile metadata? Yes. While ICC profiles are not descriptive metadata like EXIF or IPTC, they are a critical form of technical metadata embedded in the image file header.

An ICC (International Color Consortium) profile defines the image's color space — the rules for how RGB number values should be translated into actual colors on a display or in print.

Common Color Profiles

Profile	Gamut	Best For
sRGB	Standard	Web, social media, most screens
Adobe RGB (1998)	Wider	Print, professional photography
ProPhoto RGB	Widest	Archival, high-end retouching
Display P3	Wide	Modern Apple devices, HDR content

Why It Matters

Without an ICC profile, a color-managed application has no way to know how to interpret the pixel values. The same RGB triplet (180, 50, 20) will render as noticeably different colors depending on whether the image is tagged sRGB or Adobe RGB. This is why images with Adobe RGB profiles often look washed out on the web — browsers assume sRGB if no profile is present.

Privacy Risks of Image Metadata

The most serious concern with image metadata is unintentional information disclosure. When you share a photo, you may be revealing far more than the image itself.

What Can Be Exposed?

Exact GPS coordinates of where the photo was taken — potentially your home, workplace, or child's school
Date and time patterns that reveal your daily routine
Device fingerprint (camera make, model, serial number) that can link photos across platforms
Software and editing history via XMP data

Real-World Incidents

One of the most notable cases: in 2012, cybersecurity pioneer John McAfee was on the run in Belize when a journalist posted a photo of him. The EXIF GPS data in the image pinpointed his exact location in Guatemala, and authorities used it to track him down and arrest him within hours. (Proton) (EDUCAUSE Review)

The U.S. National Security Agency (NSA) has published guidance specifically warning about the risks of location metadata in photos, recommending that sensitive operations disable geotagging entirely. (NSA - PDF)

Do Social Media Platforms Protect You?

Most major platforms strip EXIF data from the publicly visible version of your photos:

Platform	Strips EXIF for viewers?	Retains original on servers?
Facebook	Yes	Yes — used for ad targeting
Instagram	Yes	Yes — retained by Meta
Twitter/X	Yes	Unclear
WhatsApp	Yes	End-to-end encrypted

Important caveat: While other users cannot see your EXIF data, the platforms themselves often retain the original file with all metadata on their servers for internal use. Stripping metadata before uploading is the only way to ensure it never reaches the platform at all.

How to View, Remove, and Edit Metadata

Viewing Metadata

To inspect what metadata an image contains:

Online: Use Image Size Finder to upload images and view all EXIF, GPS, IPTC, XMP, and ICC profile data organized by category — everything runs in your browser.
Desktop: ExifTool by Phil Harvey is the gold standard command-line tool for reading metadata from virtually any image format.
Mobile: Apps like EXIF Viewer (iOS) or Photo EXIF Editor (Android) can read metadata from your camera roll.

Removing Metadata

To strip all metadata before sharing:

Online: Use Image Size Finder's Metadata Remover — 100% browser-based, no upload to any server. Supports JPEG (lossless), PNG, WebP, and all browser-renderable formats.
Windows: Right-click → Properties → Details → "Remove Properties and Personal Information"
macOS: Use Preview → Tools → Show Inspector → remove GPS data, or use ExifTool in Terminal
Command line: exiftool -all= photo.jpg strips all metadata in one command

Editing Metadata

Sometimes you need to modify metadata rather than remove it — for example, correcting a wrong date or adding copyright information:

Online: The Metadata Remover Editor tab lets you edit Date Taken, Author, Copyright, and Description fields in JPEG files, entirely in the browser.
Desktop: Adobe Lightroom, Adobe Bridge, or ExifTool for batch operations

Metadata by Image Format

Not all image formats support all metadata standards equally:

Format	EXIF	IPTC	XMP	ICC Profile
JPEG	Full	Full	Full	Yes
TIFF	Full	Full	Full	Yes
PNG	Limited	No	Yes (via iTXt)	Yes
WebP	Yes	No	Yes	Yes
HEIC/HEIF	Full	Limited	Yes	Yes
AVIF	Yes	No	Yes	Yes
GIF	No	No	Limited	No
SVG	N/A	N/A	Yes (XML-native)	N/A

JPEG and TIFF have the most comprehensive metadata support, which is why they remain the preferred formats for professional photography workflows. (Library of Congress) (Google Developers - WebP)

Summary

Standard	Created By	Purpose	Editable?
EXIF	CIPA/JEITA (1995)	Camera technical data	With tools
IPTC	IPTC (1990)	Editorial / rights	Yes, by design
XMP	Adobe (2001, ISO 2012)	Processing + extensible	Yes, by design
ICC Profile	ICC	Color space definition	Rarely needed

Image metadata is powerful — it enables photo management, copyright protection, and color accuracy. But it also carries real privacy risks. Understanding what's in your images and how to control it is an essential skill for anyone who shares photos online.

Try it yourself: Upload an image to Image Size Finder to see all its metadata, or use the Metadata Remover to strip it before sharing.

DEV Community: Stone

Markdown Viewer – A Fast, Privacy-First & Feature-Rich Online Editor

Why Another Markdown Editor?

Key Features at a Glance

1. 100% Client-Side Privacy & Zero Setup

2. Math & Diagram Powerhouse

3. 50+ Custom Themes & Social Publishing

4. Versatile Import & Export Options

5. Developer-Friendly Editor Experience

The Tech Stack

What’s Next? (Roadmap)

Try It Out & Share Your Feedback

What is Image Metadata?

What is Image Metadata?

The Three Major Metadata Standards

1. EXIF (Exchangeable Image File Format)

2. IPTC (International Press Telecommunications Council)

3. XMP (Extensible Metadata Platform)

How They Work Together

ICC Profiles: The Color Metadata

Common Color Profiles

Why It Matters

Privacy Risks of Image Metadata

What Can Be Exposed?

Real-World Incidents

Do Social Media Platforms Protect You?

How to View, Remove, and Edit Metadata

Viewing Metadata

Removing Metadata

Editing Metadata

Metadata by Image Format

Summary

Sources