minify-html does not have any error states and will always output a value. This means that all possible ambiguous or malformed states need to be handled. This document describes these.
minify-html tries to match what the specs dictate and modern browsers do. However, there may be occasional differences for malformed syntax, as the browser and spec rules are very complex when handling invalid HTML.
To see some complex inputs, check out the various fuzzing inputs.
- Input must be valid UTF-8 without BOM.
- All HTML is interpreted as HTML5.
- Escaped and double-escaped script content are not supported.
If the input ends while in the middle of a tag or attribute value, that tag/attribute is closed, as well as all ancestor tags.
| Rule | Example source | Example interpretation |
|---|---|---|
A tag name is one or more alphanumeric, :, or - characters |
<x:a:b:--d09> |
<x:a:b:--d09> |
script, style, textarea, and title tags do not close until the case-insensitive sequence </ followed by the tag name. |
<teXTaRea></textare></TEXTArea> |
<textarea></textare></textarea> |
| Attribute-like syntax in closing tags are parsed like attributes but ignored. | <div></div x=">">5 |
<div></div> |
If the character following </ is not a valid tag name character, all code until the next > is dropped. It is not considered a closing tag, even as an invalid one. |
<div></ div x=">">5 |
<div>">5 |
| If a closing tag represents a void element, the closing tag is dropped. | <div><br>ax</br><img></img>i</div> |
<div><br>ax<img>i</div> |
| If a closing tag does not match the opening tag, and the closing tag cannot be omitted as per the spec, the closing tag is ignored. NOTE: Most browsers have far more complex logic. | <div><span></div></span>5 |
<div><span><span>5 |
If an opening tag ends with /> instead of >, and it's an HTML tag, the / is ignored. If it's an SVG tag, it's self-closing. |
<div/>5<div></div> |
<div>5<div></div> |
A slash as the last character of an unquoted attribute value immediately preceding a > is not interpreted as part of the self-closing syntax />, even for self-closable SVG elements. |
<circle r=1/> |
<circle r="1/"> |
Any opening html, head, or body tags after the first are ignored. |
<html><head><meta><body><div><head><span><body> |
<html><head><meta><body><div><span> |
Any closing html or body tags, or head after the first, are ignored. |
<html><head><meta><body><div></body><span></body><input></html><a> |
<html><head><meta><body><div><span><input><a> |
If a < in content is not followed by an alphanumeric, :, or = character, it is interpreted as a literal <, as per the spec. |
<div>< /div>< span> |
<div>< /div>< span> |
| Rule | Example source | Example interpretation |
|---|---|---|
Whitespace can exist between an = and the attribute name and value. |
a = =b= |
a="=b=" |
An unquoted attribute value continues until the next > or whitespace character. |
a = b"cdef/> |
a='b"cdef/'> |
Whitespace and slashes separate attributes, but not around =. |
a = b /c/d==/e=/f |
a="b" c="" d="=" e="/f" |
An attribute name starts with any character other than a whitespace, /, or > (= is allowed) and continues until the next =, /, >, or whitespace character. |
== "a": {}#$'=/> |
=="" "a":="" {}#$'="" /> |
| If multiple attributes exist with the same case-insensitive name, only the last is kept. | a=b a=c b=c a=d |
b=c a=d |