By Alexandre Alapetite on 2006-03-24; updated on 2012-07-28

General XHTML and XML validator

Weblide is a general multi-schema XML validator, freeware, capable of browsing a whole XHTML Web site online or locally, and supporting XHTML5. It is also a powerful link checker.

It is targeted to Web masters with some knowledge of XML standards, but the predefined profiles make it suitable from beginners to experts.

Weblide can use at the same time DTD, XML schemas (XSD), RELAX NG and Schematron to validate against. The software comes with a predefined list of schemas for most cases, but advanced users can extend this list themselves. The schemas and their inclusions are automatically downloaded once from their Internet location, and cached locally.

While being mostly based on official schemas, Weblide is stricter (except for XHTML5), checks many more things than e.g. the W3C validator for XHTML, and supports many other types of XML documents.

  ➟ Download Weblide validator


[Home]. [Output details]. [Validation settings]. [Robots settings]



Validation technologies

Major supported schemas

W3C official schemas: XHTML5 [RELAX NG, Schematron], XHTML1.x [DTD, XSD, Schematron], RDF (partial) [RELAX NG], MathML [DTD, XSD], P3P [XSD], SOAP [XSD], SPARQL Query Results XML Format: [XSD, RELAX NG], SVG: [DTD (≤1.1), RELAX NG], VoiceXML: [DTD, XSD], WSDL: [XSD], XML Schema (XSD): [DTD, XSD], XML Signature: [DTD, XSD].

Other official schemas: Atom 1.x [RELAX NG], Dublin Core [XSD], Google sitemaps [XSD], MediaWiki [XSD], RELAX NG [RELAX NG, Schematron], Schematron 1.5 [DTD, Schematron].

Third party schemas: WAI WCAG 1.0 accessibility with Schematron adapted from Petr Nalevka, XSLT 1.0 with RELAX NG from James Clark, RSS 1.0 with Schematron from Leigh Dodds.


Distribution notes

Weblide requires the .NET 4.0 client framework (also available with Windows update).

Alternatively, in particular under Linux, you can try Mono.
In particular with Mono, you may download the previous version 2.0 of Weblide (.NET 2.0, partial support since Mono 1.2.5).

Most of the needed schemas will be downloaded from the Web the first time they are used. In addition, Weblide is packaged with a few schemas in ./weblide/modified-schemas/; those are corrections of schemas that contained errors, that needed modifications to work with Weblide, or schemas designed especially for Weblide.

Warning: You should avoid running this software on production Web sites, and rather use it on your own development machine, as this software can potentially be harmful when for instance it follows some dynamic links that are making actions on the Web site. By downloading this software, you agree that the developer is not responsible for any consequence of its use or misuse.


If you use and like this software (especially for professional purposes), please consider doing a donation.

Current Limitations

Frequently Asked Questions

The program does not start

  1. Have you installed the .NET 4.0 framework? (also available with Windows update)

XML encoding error

Symptoms: The validator raises an Unicode error, or an XML error about an invalid character, and/or a conflict between charsets.

Description: Weblide does not deal with HTML tag soup, but only with pure XHTML, that is to say XML compliant. Here is the standard behaviour when no encoding is declared in the HTTP headers:

application/xhtml+xml ou application/xml
The encoding is detected with the Unicode BOM and the XML declaration. In their absence, UTF-8 is used.
The encoding used is US-ASCII and is authoritative over the XML declaration.
The encoding used is ISO-8859-1. the old declaration <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /> is not used.

Solution: Have a look to the “Output details” tab, where you can see which character set is declared by your Web server if any (subtitle “HTTP + Unicode”) and which one is been used (subtitle “XML + Unicode”). In order to have valid XHTML+XML documents, you must:

  1. Have a correct HTTP Content-Type header with a declaration of the character set. Those have highest priority.
  2. And/or for application/xhtml+xml or application/xml documents:
  3. And/or use the default encoding or the one declared in HTTP headers.

It is a good idea to follow all of those three rules (where you can replace "ISO-8859-1" by e.g. "UTF-8").
Read more at the W3C:

XHTML specific errors

Legend in fieldset

The legend element in fieldset is mandatory in XHTML 1.0 strict according to the official XML schema (on purpose), but optional in the DTD. The specification says that legend should be used to improve accessibility.

If you don’t believe the results

Weblide is almost only an engine that validates documents against external schemas, and most of those are official and normative. For XHTML pages, please try other validation services before blaming this software:


2.3 beta 2012-07-28
Increased support of XHTML5
Update of the schema database
.NET 4.0 Client Profile
Many other improvements and updates
2.0 beta 9.2 2007-07-15
New RELAX NG schema for Mozilla Microsummaries
2.0 beta 9.1 2007-06-16
New schema for Schematron ISO
New experimental schema (“expert” mode) for some additional constraints in HTML 5
2.0 beta 9 2007-06-04
New and updated schemas (SPARQL, WSDL, XHTML, WAI, etc.)
Support and validation of xml-stylesheet
Schematron validation for XHTML element prohibitions
Alphabetic sorting of URL parameters to minimise redundant dynamic addresses
For Linux, partial support of Mono, since its version 1.2.5
2.0 beta 8 2006-11-05
Minor modifications of schemas
2.0 beta 7 2006-06-11
Contextual menu to copy error messages or open invalid pages in the browser
Improvement of SchemaDB.xml and SchemaDB.xsl
Update for XHTML Basic 1.1 according to the new specification, and related schemas such as XHTML+Voice
Include new corrections for errors in W3C schemas
2.0 beta 6 2006-05-14
Better messages for encoding errors
2.0 beta 5 2006-05-13
For documents with a MIME media type text/html, the default encoding is now "ISO-8859-1"
2.0 beta 4 2006-05-12
Multiple sources Schematron validation with the XSLT function document()
Stricter Unicode validation for documents which encoding is declared in HTTP headers
Added a tab to manage the cache
Improvement of SchemaDB.xsl
2.0 beta 3 2006-05-02
Allow multiple Schematron schemas per document
Use Schematron instructions embedded in XSD and RELAX NG schemas
Added support for xsi:noNamespaceSchemaLocation in addition to xsi:schemaLocation
2.0 beta 2 2006-04-23
Corrected issue with Schematron and documents containing <element attribute="&quot;"/>
Improvement of WAI schema
Added RELAX NG schemas for DSDL
Added DTDs for XHTML+Voice with many corrections
2.0 beta 1.3 2006-04-20
Atsushi Eno update of RELAX NG to discard Schematron instructions without error
Correction for /robots.txt
DTD system is no longer displayed in the “output details” tab when DTD validation is disabled
2.0 beta 1.2 2006-04-06
Corrections in Dublin Core schemas when they are used with XHTML
Small updates in SchemaDB.xml
2.0 beta 1.1 2006-04-05
Update of SchemaDB.xsl to allow even more foreign namespaces together
Corrections in MathML schemas to use full XLink
Additional tests in Schematron for XHTML
Weblide can now receive arguments from e.g. the command line, or the “send to” menu
Better catch of some errors
2.0 beta 1 2006-04-04
Initial Weblide public release
2.0 trunk 2005-12-08
New start from scratch
2002-2004 ValideXHTML 1.x
Ancestor "ValideXHTML" 1.x


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