Convert BBCode to HTML

Paste text containing bold, italic, underline, URL, quote, or list markup and receive an HTML string that is ready for controlled use in a page or publishing workflow. Recognized tags may be nested, ordinary HTML characters are escaped, and malformed nesting is reported instead of silently producing broken markup. The conversion is deterministic, requires no network access, and returns the same result for the same input every time.

Convert the supported BBCode tags

The converter recognizes six familiar BBCode families: <code>[b]</code>, <code>[i]</code>, <code>[u]</code>, <code>[url]</code>, <code>[quote]</code>, and <code>[list]</code>. Bold becomes <code>&lt;strong&gt;</code>, italics become <code>&lt;em&gt;</code>, underline becomes <code>&lt;u&gt;</code>, quotations become <code>&lt;blockquote&gt;</code>, and lists become unordered HTML lists with list items. A link can use either <code>[url=https://example.com]label[/url]</code> or <code>[url]https://example.com[/url]</code>. List entries begin with <code>[*]</code> inside a list. Tags can be nested when they close in reverse order, so bold text can contain italics or a link label can contain ordinary characters. Tags outside this supported set are preserved as escaped text rather than interpreted as HTML. That narrow contract makes the result easy to reason about and avoids pretending to support the many incompatible BBCode extensions used by different forum packages. If a source relies on custom color, size, image, table, or media tags, handle those separately before or after this conversion with rules appropriate to that source.

Understand validation and safe output

Recognized BBCode must be structurally balanced. Every opening formatting tag needs the matching closing tag, nested tags must close in the opposite order from which they opened, and list item markers must occur directly within a list. A malformed sequence returns an invalid-input error instead of a partial document. This matters in automated publishing because silently repaired markup can move emphasis, links, or quoted material across boundaries the author did not intend. Plain text is HTML-escaped during rendering, including angle brackets and ampersands, while link destinations are escaped for attribute use. Explicit URL schemes are limited to HTTP, HTTPS, and mailto; fragment links and relative destinations are also accepted. This scheme check prevents a BBCode link from becoming an obvious script URL, but the output should still pass through the security and content policy used by the application that embeds it. The converter is a syntax transformer, not a complete trust boundary or a replacement for a site-specific HTML sanitizer, permission system, or moderation process.

Use the result in a publishing workflow

Send one <code>text</code> value and read the converted markup from the returned <code>html</code> field. This simple shape works well in migration scripts, forum exports, comment pipelines, knowledge-base imports, and test fixtures. Before converting a large archive, sample records from the actual source platform because BBCode dialects differ: some use numbered-list arguments, special quote attributions, or proprietary media tags that are intentionally outside this capability. Keep the original BBCode alongside the converted result until the migration has been reviewed, making it possible to adjust source-specific preprocessing without losing information. In an interactive editor, surface an unbalanced-tag error near the author rather than discarding their formatting. In a batch import, record the failing item and continue according to your own retry policy. Conversion via the API costs $0.002 per item, while the deterministic implementation makes repeated runs stable. Because no network, clock, randomness, or external service participates, the same accepted input produces byte-for-byte equivalent HTML across runs.