# Common HTML Issues

> Canonical HTML version: https://rocketvalidator.com/docs/api/common_html_issues
> Attribution: Rocket Validator (https://rocketvalidator.com)
> License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

Typically, the same kind of issue affects many Web Pages on a given Report. For example, the issue <code>"The “center” element is obsolete. Use CSS instead."</code> may affect many Web Pages on the same report.

A Common HTML Issue represents a given HTML Issue that is common to many Web Pages, thus showing its details, how many times it's found on the Report, and links to the related Web Pages.

## Attributes

<dl>
  <dt>ID</dt>
  <dd>Unique ID for this Common HTML issue.</dd>

  <dt>Report ID</dt>
  <dd>Id of the related report.</dd>

  <dt>Issue Type</dt>
  <dd>Error or Warning</dd>

  <dt>Issue Sub Type</dt>
  <dd>Optional, provides additional info on the type of the issue.</dd>

  <dt>Message</dt>
  <dd>Brief description of the issue.</dd>

  <dt>Tags</dt>
  <dd>Comma-separated list of tags to categorize this issue.</dd>

  <dt>How Many</dt>
  <dd>Total times this issue has been found in the web pages for the report.</dd>

  <dt>Description</dt>
  <dd>Short plain-text explanation of the issue, from the Rocket Validator guide that matches it. Null when no guide matches.</dd>

  <dt>Description Markdown</dt>
  <dd>The same explanation in Markdown. Null when no guide matches.</dd>

  <dt>Description HTML</dt>
  <dd>The same explanation as rendered HTML. Null when no guide matches.</dd>

  <dt>Guide URL</dt>
  <dd>Link to the full guide for this issue. Null when no guide matches.</dd>
</dl>


> **Guide descriptions are not available for every issue**
>
> Rocket Validator publishes a guide for the most common issues, but not for
> every possible validator message. When no guide matches an issue, the four
> description and guide attributes are `null`. Treat them as optional.

## Relationships

<dl>
  <dt>Web Pages</dt>
  <dd>The list of Web Pages affected by this issue.</dd>
</dl>

## Example


> **Example: Common HTML Issue**
>
> ```json
> {
>   "data": {
>     "attributes": {
>       "description": "Each HTML element must have unique attribute names \u2014 no attribute can appear more than once on the same element.",
>       "description_markdown": "Each HTML element must have unique attribute names \u2014 no attribute can appear more than once on the same element.",
>       "description_html": "<p>Each HTML element must have unique attribute names \u2014 no attribute can appear more than once on the same element.</p>",
>       "guide_url": "https://rocketvalidator.com/html-validation/duplicate-attribute-x",
>       "how_many": 132,
>       "issue_sub_type": null,
>       "issue_type": "error",
>       "message": "Duplicate attribute \u201cid\u201d.",
>       "report_id": "72eecced-8472-41fc-b194-59b7496c7576",
>       "tags": [
>         "duplicate attribute"
>       ]
>     },
>     "id": "144375908",
>     "relationships": {
>       "web_pages": {
>         "links": {
>           "related": "https://rocketvalidator.com/api/v1/reports/72eecced-8472-41fc-b194-59b7496c7576/web_pages?filter[common_html_issue_id]=144375908"
>         }
>       }
>     },
>     "type": "common_html_issue"
>   },
>   "jsonapi": {
>     "version": "1.0"
>   }
> }
> ```

## List Common HTML Issues on a Report

To list the Common HTML issues found on a report, send a `GET` request to `/api/v1/reports/$REPORT_ID/common_html_issues`.


> **Example: list the Common HTML issues found on a report**
>

	```
	GET /api/v1/reports/$REPORT_ID/common_html_issues
	```

### Filtering by message

To include only the HTML issues of a given kind, use the `filter[message]` option.


> **Example: filter HTML issues for a report about "table"**
>
> ```
> GET /api/v1/reports/$REPORT_ID/common_html_issues?filter[message]=table
> ```

### Filtering by tag

To include only the issues for a given `tags` combination, use the `filter[tags]` options:

* `filter[tags][mode]` setting the tag combination mode, which can be `any`, `all` or `none`.
* `filter[tags][list]` including a comma-separated list of tags.


> **Example: filter HTML issues for a report tagged with "label"**
>
> ```
> GET /api/v1/reports/$REPORT_ID/common_html_issues?filter[tags][mode]=any&filter[tags][list]=label
> ```

## Retrieve a Common HTML Issue

To retrieve a Common HTML Issue on a given Report, send a GET request to `/api/v1/reports/$REPORT_ID/common_html_issues/$COMMON_HTML_ISSUE_ID`.


> **Example: retrieve a Common HTML issue on a report**
>

	```
	GET /api/v1/reports/$REPORT_ID/common_html_issues/$COMMON_HTML_ISSUE_ID
	```

## List the Web Pages affected by a Common HTML Issue

To list the Web Pages that are affected by a given issue, refer to <a href="https://rocketvalidator.com/docs/api/web_pages#filtering-by-html-issue">Filtering by HTML issue</a> on the Web pages endpoint.