Can I run JavaScript in the preview?

The iframe uses sandbox=\"allow-same-origin\" without allow-scripts, so JavaScript won’t execute. This is a deliberate safety measure. The editor is for HTML and CSS preview only.

Is the preview sandboxed from the main page?

Yes. The preview renders inside an iframe with a srcdoc attribute, which isolates it from the parent page. Your experimental HTML and CSS cannot break the tool interface or leak styles into the surrounding page.

HTML Editor

About HTML Editor

A browser-based HTML code editor with live preview rendered in a sandboxed iframe. Includes three starter templates (basic HTML5, responsive layout, contact form), auto-formatting that indents tags by nesting depth, undo/redo history, and structural validation that checks for DOCTYPE, html, head, body, and title tags. A stats bar shows character count, line count, tag count, and file size in bytes.

Live preview uses a sandboxed iframe (allow-same-origin) that updates as you type
Validation checks for DOCTYPE, <html>, <head>/<body> completeness, and <title> presence
Auto-formatter splits adjacent tags onto separate lines and indents by nesting depth
Three templates: Basic HTML5 skeleton, Responsive (with CSS media queries), and Contact Form
Download exports as a text file; character/line/tag/byte stats update in real time

Frequently Asked Questions

Can I run JavaScript in the preview?: The iframe uses sandbox=\"allow-same-origin\" without allow-scripts, so JavaScript won’t execute. This is a deliberate safety measure. The editor is for HTML and CSS preview only.
Is the preview sandboxed from the main page?: Yes. The preview renders inside an iframe with a srcdoc attribute, which isolates it from the parent page. Your experimental HTML and CSS cannot break the tool interface or leak styles into the surrounding page.

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Fuel Economy Calculator — Calculate MPG or L/100km from distance and fuel used.
Graphing Calculator — Plot mathematical functions and equations on a graph.
IP Address Calculator — IPv4 subnet calculator: network, broadcast, mask, host range, special-use scope, binary, and subnet splitting.
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Percentage Calculator — Find percentages, percent change, and what percent X is of Y.
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Time Zone Calculator — Convert times between different time zones.
Unit Price Calculator — Compare prices per unit to find the best deal.

Converters

Binary Text Converter — Convert text to binary and binary to text.
CIDR to IP Range Converter — Convert CIDR notation to IP address ranges.
Color Code Converter — Convert colors between hex, RGB, HSL, and CMYK.
CSV to JSON Converter — Convert CSV data to JSON format.
Data Storage Converter — Convert between bytes, KB, MB, GB, TB, and more.
JSON to CSV Converter — Convert a JSON array of objects to CSV — nested keys flattened, columns merged, values RFC-4180 escaped.
JSON to YAML Converter — Convert between JSON and YAML in both directions, with auto-detection — for configs, pipelines, and manifests.
Markdown to HTML Converter — Convert Markdown to HTML.
Number Base Converter — Convert numbers between binary, octal, decimal, hexadecimal, and any custom base 2–36.
Roman Numeral Converter — Convert between Roman numerals and regular numbers.
Time Converter — Convert between hours, minutes, seconds, and more.
Unit Converter — Convert length, weight, temperature, and other units.
URL Encoder Decoder — Encode and decode URL strings.

Date & Time

Countdown Timer — Count down to any date or event.
Stopwatch — Stopwatch with lap times.
World Clock — See current time in cities around the world.

Development

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Cron Expression Builder — Visually build cron expressions by clicking checkboxes and dropdowns — no syntax memorization required.
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Regex Pattern Explainer — Explain what a regex pattern does in plain English.
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Flashcard Maker — Create flashcards for studying and memorization.
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Typing Speed Test — Test your typing speed and accuracy.

Finance

Breakeven Calculator — Calculate breakeven point, margin, and target profit.
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