Html Tools

Browse all available html tools.

Available tools

abbr title A11y Note Lookup Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
accesskey Browser Conflict Note Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
Anchor download Filename Attr Serializes a suggested filename into a double-quoted anchor download attribute. Empty filename requests downloading without a suggested name. Browser origin policy and filesystem filename sanitization are separate.
Anchor target Values Lookup Classifies standard HTML navigable target keywords or valid named targets. Empty values default to the current context. Browser-specific target extensions are excluded.
apple-touch-icon iOS Sizes Lookup Bounded common square pixel icon hints; actual device/browser recommendations vary and no complete current iOS table asserted.
ARIA State Attribute Pair Check Checks a WAI-ARIA 1.2 state attribute name and a defined value token in recommended lowercase author spelling. This exact-spelling lexical pair check does not evaluate browser error recovery, role applicability or accessibility.
aria-live polite/assertive/off Lookup Classifies aria-live priorities: polite waits for an appropriate idle opportunity, assertive may interrupt, and off permits updates associated with focus. Actual assistive-technology announcements are not guaranteed.
audio preload metadata/none/auto Values Resolves audio preload hints none, metadata or auto, with empty present value mapping to auto. Both omitted and invalid attributes are implementation-defined; this does not predict network buffering.
autocomplete Standard Tokens Lookup Classifies individual standard autocomplete tokens as field, contact qualifier, address qualifier, section, mode, credential or unknown. Whole-attribute order and control applicability need a separate check.
b/i vs strong/em Semantic Split Classifies b, i, strong and em by standard meaning: attention, alternate voice, importance or stress emphasis. Font weight and style are not inferred.
base href Single Instance Warning Reports multiple base elements with href attributes and the first such href in document order. Include empty href attributes in the vector. This checks cardinality and selection only, without URL resolution or base target attributes.
Boolean Attributes List Lookup Looks up current standard HTML boolean attribute names, independent of their element applicability. Enumerated hidden, draggable and contenteditable are excluded.
br vs wbr Break Opportunity Diff Distinguishes a br line break from a wbr line-break opportunity. Both are void elements; actual line wrapping depends on layout.
Button Default type=submit Note Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
Canonical link rel Check Checks the canonical relation and a nonempty parsed href. Relative href values are accepted; this does not establish URL validity or canonical selection by search engines.
Canonical vs og:url Duplication Note Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
Canvas Fallback Content Note Determines canvas fallback in interactive visual media from caller-supplied canvas support and scripting state. Disabled scripting or disabled canvas support displays fallback. Printing/static media and accessibility subtree behavior are outside this profile.
caption vs summary Deprecated Lookup Classifies a table caption element versus the obsolete summary attribute for current authoring conformance. This reports syntax status and caption semantics only.
cite/q/blockquote Inline-Block Classify Classifies cite, q and blockquote by standard content category and meaning. Phrasing content is reported rather than a CSS display guarantee.
colgroup span Count Calculator Counts colgroup columns from normalized positive spans (at most 1000 each). When col children exist their spans determine the count and a group span attribute is nonconforming.
contenteditable Inheritance Behavior Resolves contenteditable attribute state and whether ordinary element contents are editable using a caller-supplied inherited editable flag. Empty means true and invalid/omitted values inherit. DesignMode, rich-formatting inheritance and unrelated inertness are separate.
crossorigin anonymous/use-credentials Table Resolves a CORS settings attribute and potential-CORS request credentials mode for img/media without the same-origin fallback flag. Missing attribute means no-cors/include; empty or invalid present values mean cors/same-origin. Always-CORS features use a different mapping.
Custom Element Dash-Name Requirement Validates custom-element names using the current HTML and DOM local-name rules: initial ASCII lowercase, a dash, no ASCII uppercase or forbidden local-name characters, and no reserved SVG/MathML names. This does not check registry availability.
data-* Attribute Naming Validator Validates a namespace-less DOM data-* attribute local name and derives its dataset property name. Supply the DOM name after any HTML parser lowercasing.
datalist Combobox Pattern Lookup Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
details/summary Native Disclosure Reports whether details body content is exposed by the open attribute and which direct summary element is the native summary (the first one). Structural placement is reported separately from disclosure state.
dialog::backdrop Open Method Lookup Classifies closed, show/open nonmodal and showModal modal dialog states. Only modal dialogs enter the top layer and have a backdrop; actual appearance depends on CSS.
dir=auto First-Strong Heuristic Explicit bounded heuristic for ASCII Latin L and Hebrew/Arabic strong letters; skips numbers/punctuation/marks, reports unsupported strong-script evidence rather than pretending full Unicode bidi.
dns-prefetch rel Usage Lookup Identifies dns-prefetch in a parsed link relation and a supplied nonempty href. This classifies the hint only and performs no DNS or URL validation.
embed/object Legacy Deprecation Note Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
Favicon link rel sizes Lookup Checks parsed link rel and icon sizes tokens against the standard any or positive width x height syntax without leading zeros. Dimensions are returned as exact decimal strings.
fieldset/legend A11y Pair Check Checks a fieldset direct-element-child list for a single legend in first position. A legend is optional in HTML; this check reports the structural pairing without claiming complete accessibility.
figure/figcaption Pairing Check Checks figure direct-element children for at most one figcaption at either end. Missing figcaption is allowed; caption content quality and accessibility are outside this structural check.
Global Attributes List Lookup Looks up named HTML global attributes including DOM class, id and slot. Separately identifies data-* and aria-* families without validating individual family names or event handlers.
Heading Level h1–h6 Order Sequence Check Finds adjacent upward jumps greater than one in supplied heading levels. Returns zero-based positions; this outline heuristic does not establish a WCAG failure.
hidden=until-found Find-In-Page Lookup Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
hr Thematic Break Semantics Identifies hr as a paragraph-level thematic break in a list of parsed HTML element names. A rendered horizontal line alone does not establish these semantics.
hreflang Alternate Language Pairs Checks supplied hreflang/href pairs for nonempty values and repeated language labels ignoring ASCII case. It does not validate BCP 47 registry membership, URL syntax, reciprocal links or search-engine selection.
HTML Attribute Occurrence Duplicate Audit Audit duplicate attribute occurrences under HTML ASCII name lowercase without parsing a tag or losing duplicates; supplied occurrence indexes remain observable.
HTML Attribute Occurrence Last Wins Apply an explicit last-occurrence-wins policy to supplied HTML attribute observations, preserving winning source indexes; browsers’ tokenizer normally uses first wins instead.
HTML Attribute Parser Lexically parse one HTML start tag into its lowercase name and attributes, retaining raw character references and the first duplicate attribute.
HTML Attribute Quote Choice Budget Compare serialized UTF-16 budgets for single- and double-quoted escaped HTML attribute values, including surrounding quotes; not a security or byte-size guarantee.
HTML Attribute Token Value Escape Escape an explicit HTML quoted attribute value for a selected quote character, including ampersand and angle brackets; not a URL, script or style sanitizer.
HTML Class Token Difference Subtract literal HTML class tokens while preserving surviving duplicates and order; CSS selector syntax and case folding are not applied.
HTML Class Token Duplicate Audit Audit class token duplicates using HTML ASCII whitespace splitting and exact case-sensitive token identity; does not parse selectors or CSS escapes.
HTML Class Token Stable Merge Merge explicit HTML class attribute strings as stable exact token union after ASCII whitespace tokenization; preserve first token appearance.
HTML Comment Remover Remove lexical HTML comments while preserving comment-like text inside script, style, title, and textarea elements.
HTML Data Key Camel Dash Transform Convert a valid dataset key to an HTML data-* attribute name, inserting dashes before ASCII uppercase letters; dash-lowercase keys are rejected under DOMStringMap rules.
HTML Data Name Dash Camel Transform Convert a supplied HTML data-* attribute name to its dataset key using ASCII lowercase then dash-lowercase camelization; no Unicode case folding or DOM mutation.
HTML ID Reference Ambiguity Audit Inventory all supplied document ID positions matching each explicit ID-reference token and identify ambiguity instead of arbitrarily choosing the first element.
HTML ID Reference Token Coverage Audit an explicit HTML ID-reference token list against supplied document IDs, retaining unknown references and repeated tokens; not DOM traversal or an accessibility certification.
HTML Ordered List Counter Sequence Calculate ordered-list counters with explicit start, reversed/default-start policy and per-item integer value overrides; operates on supplied item records, not a DOM tree.
HTML Table Cell Span Occupancy Map Build an occurrence-preserving HTML cell-span owner map at explicitly supplied source coordinates for one row group; rowspan zero reaches that group’s end, no automatic browser table placement.
HTML Tag Counter Count lexical HTML start tags while ignoring comments, declarations, closing tags, and apparent tags inside raw-text elements.
HTML Tag Stripper Remove lexical HTML tags, comments, and declarations while retaining raw text and character references; the result is not sanitized markup.
HTML Text Extractor Extract lexical HTML text while excluding script and style contents, decoding numeric and common syntax references, and preserving unknown named references.
HTML Whitespace Collapser Collapse ASCII whitespace in lexical text nodes while preserving tags, attributes, comments, and preformatted or raw-text element contents.
iframe loading=lazy Support Lookup Resolves an iframe loading attribute to eager or lazy and reports whether lazy loading is eligible given caller-supplied browser support and scripting state. Actual viewport scheduling remains browser controlled.
iframe sandbox Token List Lookup Classifies standard iframe sandbox tokens and resolves the scripts and origin restrictions imposed by this attribute alone. Omitted sandbox differs from an empty sandbox; inherited and CSP restrictions are outside this check.
img alt Presence Checker Checks whether a parsed img has an alt attribute and whether its value is empty. Empty alternative text can be appropriate for decorative images; this is a presence check only.
img decoding async/sync/auto Hint Resolves img decoding sync, async or auto hints with auto as missing and invalid default. Actual decoding strategy remains a user-agent decision.
img loading eager/lazy Default Resolves img loading keywords with eager as both missing and invalid default. This reports the hint and does not guarantee actual lazy deferral.
inert Focus Suppression Lookup Resolves inert attribute restrictions from own and inherited flat-tree inertness. A modal dialog opened with showModal escapes inherited inertness, while its own inert attribute still applies. Other disabling and focus rules are separate.
Inline SVG vs object Tradeoff Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
Input Type Mobile Keyboard Map Bounded common mobile input-type keyboard hints, not device-specific layout guarantees.
Input Types Full List Lookup Looks up all 22 standard input type keywords and resolves unknown or missing values to text. Keyword matching is ASCII case insensitive without trimming.
label for=id Binding Check Resolves explicit label for binding from document-order IDs and labelability flags. An explicit for attribute uses the first matching ID; a nonlabelable first match prevents binding to a later duplicate.
lang Attribute BCP-47 Checker Bounded BCP47 syntax including extlangs, scripts/regions, variants, extensions/private use and grandfathered tags; no IANA registration or content-language detection.
link preload as= Types List Checks the six current HTML preload as destinations and translates fetch to the empty Fetch destination. Modulepreload has a separate vocabulary and is outside this lookup.
link rel=alternate Feed Type Lookup Builds link rel=alternate feed metadata for RSS or Atom with the standard media type and an escaped caller-supplied href. URL fetching and feed document validation are separate.
mark vs strong Difference Lookup Distinguishes contextual relevance marked by mark from importance, seriousness or urgency marked by strong. Appearance is controlled by CSS.
Meta Charset First-1024-Bytes Check Checks a supplied meta charset declaration and its exclusive ending byte offset against the first 1024 bytes rule. Byte positions must come from the original encoded HTML, not UTF-16 character offsets.
Meta Refresh seconds;url Format Builds an escaped meta refresh element from a nonnegative integer delay in seconds and an absolute HTTP(S) URL. The URL is normalized with the portable WHATWG URL helper; relative URLs and fractional-delay parser behavior are outside this builder profile.
meter optimum low/high Band Classifier Classifies a meter value against caller-supplied normalized min/low/high/max bounds and optimum. Value and optimum are clamped; optimum on a low/high boundary selects the middle optimum region.
Microdata itemscope/itemprop Pattern Classifies itemscope and parsed itemprop tokens: an item scope introduces an item and can itself be a property value of an enclosing item. This checks token presence and uniqueness, without validating vocabularies or the full item graph.
min/max/step Number Input Semantics Checks parsed number-input min/max and step constraints using exact decimal arithmetic on the canonical decimal spelling of supplied finite numbers. Supply normalized positive step (default 1) and attribute presence flags; this is an ideal decimal model, independent of browser binary floating point tolerances.
Module vs Classic Script Diff Lookup Returns standard language facts for module or classic scripts: automatic strict mode, module scope and top-level var global binding. Classic scripts can opt into strict mode separately.
MSApplication Tile Legacy Lookup Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
nofollow/sponsored/ugc Difference Lookup Classifies nofollow, sponsored and ugc link annotations according to Google Search guidance. These annotations do not suppress browser navigation.
noscript JS-Disabled Fallback Resolves HTML noscript fallback and parser treatment from the HTML parser scripting flag. With scripting enabled contents are text; with scripting disabled contents are markup. XML parsing and full content-model validation are outside this tool.
Open Graph Required Tags Check Finds missing Open Graph basic metadata properties in supplied parallel property and content vectors. Requires nonempty content; it does not fetch images or validate URLs.
picture/source Art Direction Order Chooses the first eligible picture source in document order from supplied media-match and format-support flags. Supply only source elements before the fallback img that have usable source sets. Reports selected element presence without fetching or selecting image candidates.
popover/popoverTarget Pairing Lookup Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
Positive tabindex Anti-Pattern Check Classifies an explicit parsed tabindex integer: positive values request an ordering priority, zero follows ordinary sequential order, negative requests exclusion from sequential navigation. Disabled, inert and browser focus preferences are outside this attribute-only check.
prefetch/preload/prerender Diff Lookup Distinguishes current-resource preload, future-resource prefetch and future-document prerender. Prerender uses speculation rules in this profile. Outputs describe intended work, not guaranteed browser support or network activity.
progress value/max Percent Resolves progress from parsed value/max: absent value is indeterminate, nonpositive max defaults to 1, and value is clamped into [0,max]. Indeterminate percent is represented as 0 with its explicit flag.
RDFa vs JSON-LD Head Recommendation Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
referrerpolicy Values Table Resolves a referrerpolicy attribute to its standard keyword or the empty inherited-policy state. It does not compute referrer URLs or combine document headers and noreferrer.
required/readonly/disabled Diff Table Resolves required, readonly and disabled flags for an ordinary input type. Effective disabled includes inherited fieldset state supplied by the caller. Submission eligibility concerns disabling only; name, checkedness and submitter selection are separate.
Robots Meta Content Values Lookup Resolves Google Search robots index and follow directives, including all/none and restrictive conflicts. Reports recognized boolean directives and unhandled tokens; parameterized directives are outside this profile.
role=presentation vs none Equivalence Resolves equivalent presentation/none roles on an element, including focusable or otherwise interactive elements and global ARIA conflict resolution. Reports removal of this element's own implicit semantics; required owned descendants need separate checks.
ruby/rt/rp Structure Lookup Classifies ruby as the annotation container, rt as annotation text and rp as fallback parentheses. This vocabulary lookup does not validate a complete ruby content model.
s/strike vs del/ins Edited Content Diff Classifies s as no-longer-accurate content, del/ins as edits, and obsolete strike as nonconforming. Strikethrough appearance is not interpreted as edit semantics.
script defer/async Execution Order Table Classifies execution scheduling of ordinary parser-inserted classic or module scripts. Async wins over defer; inline classic flags are ignored. This assumes scripting enabled and successful fetch/evaluation, without dynamic insertion or blocking attributes.
select/optgroup Nesting Rules Check Checks direct parent relationships for option and optgroup elements in the classic select profile. Customizable selects, datalist options and intervening div elements are outside this explicitly restricted profile.
Single h1 Per Page Rule Check Explicit caller observed h1 count against a one-h1 style rule; not a HTML parsing, standard validity or accessibility certification.
sizes Attribute Width Formula Lookup Resolves the first matching sizes clause from parsed media flags and already-resolved nonnegative CSS pixel lengths. If none matches, source size defaults to viewport width (100vw). Auto sizes and CSS parsing are outside this profile.
slot name Fallback Shadow DOM Lookup Resolves automatic named slot assignment from direct host slotable names. The first slot with a given name receives matching nodes; later same-name slots display fallback. Text nodes use the empty default name. Manual assignment is outside this profile.
small Fine-Print vs em Note Distinguishes small side comments and fine print from em stress emphasis using standard semantic flags.
source type codecs Parameter Lookup Builds a source MIME type with a quoted codecs parameter from a restricted codec-identifier profile (ASCII letters, digits, dot, underscore and hyphen). It does not identify or guarantee browser codec support.
spellcheck Tri-State Inherit Default Resolves spellcheck attribute and IDL flag using caller-supplied true, false or inherit default behavior and parent flag. Missing/invalid attributes use the default behavior, which need not inherit. This does not override user preferences or decide which text is checkable.
srcset x-Descriptor vs sizes w Classifies a single srcset descriptor using conforming author syntax. Empty descriptor means 1x; width is a positive safe integer and density a positive finite float. Width descriptors use sizes, while density descriptors do not.
Table th scope A11y Check Resolves th scope keywords to row, col, rowgroup, colgroup or automatic. Valid lexical scope does not establish correct header associations or group anchoring.
target=_blank rel=opener Security Check Resolves opener behavior requested by an anchor with target=_blank under modern HTML rules. Implicit noopener applies unless opener is present; noreferrer or noopener takes precedence.
td colspan/rowspan Grid Coverage Validator Checks explicit cell rectangles within one bounded table row group using zero-based starts and normalized colspan/rowspan. Rowspan 0 reaches the group end. At most 10,000 grid slots and 1000 cells are allowed; this does not derive cell positions from HTML.
tel: Link International Format Format bounded E.164-like digit shape as global tel URI; no country-code, number assignment or caller identity validation.
template Inert Content Note Classifies ordinary template DocumentFragment contents versus content already inserted into a document or a processed declarative shadow root. Only ordinary template contents remain in the inert template owner document; other reasons for inertness are not evaluated.
textarea/input maxlength Parity Measures an input or textarea API value in UTF-16 code units against maxlength. Supply the already-normalized API value; this does not model user-edit constraint-validation conditions or grapheme counts.
theme-color Meta Lookup Bounded HTML theme-color metadata reference; not a browser compatibility guarantee.
time datetime Machine Format Builds a valid time-element datetime value from a proleptic Gregorian date and optional local/global time. Supports date, local-datetime and global-datetime profiles with years 1 through 999999; no timezone database or date inference is used.
track kind subtitles/captions/chapters Resolves track kind with subtitles as missing default and metadata as invalid default. Empty present values are invalid. This does not validate track language or WebVTT content.
translate Attribute Inheritance Resolves translate yes/no and inherited translation mode. Empty means yes, invalid and omitted values inherit; supply true as the parent mode for a root element without an ancestor.
Twitter Card Type Tags Lookup Illustrative common Twitter/X card metadata families; required fields/platform policy can change, not a live validation service.
u Unarticulated Annotation Usage Identifies u as unarticulated non-textual annotation in parsed element names. Underlining does not give u hyperlink semantics.
Valid ARIA Role Names Lookup Classifies individual WAI-ARIA 1.2 role names in their recommended lowercase author spelling as concrete, abstract or unknown. This exact-spelling vocabulary lookup excludes extensions and browser case-insensitive processing.
Video Autoplay Muted Policy Lookup Bounded HTML feature/convention note; no full document audit or live browser compatibility determination.
Viewport Meta width=device-width Check Detects an explicit width=device-width directive in viewport content split on commas or semicolons. Reports duplicate width directives rather than simulating browser viewport resolution.
Void Elements List Checker Checks parsed HTML element names against the 13 current void elements; names are ASCII case insensitive. This does not parse markup or classify obsolete elements.
Web App Manifest link rel Lookup Checks a parsed link for the manifest relation and a nonempty href. This local check does not fetch or validate the manifest document.

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