Web Developer's Tools & Resources

Free HTML / CSS / Link Validation

In a nutshell: this page lists HTML validators (which check HTML code for standards compliance and errors), CSS validators (which check Cascading Style Sheets for errors and standards compliance), browser compatibility checkers (checks your page to see if it is compatible with various browsers), broken link (or dead links) checkers, accessibility checking (check if your web page is accessible to people with disabilities), etc. Note that this page lists both online services as well as offline tools (programs).

Disclaimer

The information provided on this page comes without any warranty whatsoever. Use it at your own risk. Just because a program, book or service is listed here or has a good review does not mean that I endorse or approve of the program or of any of its contents. All the other standard disclaimers also apply.

Free HTML Validators, XHTML Validators, Browser Compatibility Checkers

CSE HTML Validator Lite checks your HTML and XHTML web pages for syntax errors. The validator comes with a syntax highlighting editor that you can use to build your web pages as well as correct errors. When run on your documents, the validator highlights lines with potential errors in your code and gives a brief message describing the possible problems associated with that line.

You can use the W3 Consortium's HTML validator to check your web documents either by giving it your web page's URL or uploading your document directly to the validator. Many people consider it the authoritative source for checking your web pages for standards compliance (since the W3 Consortium is responsible for the various HTML/CSS standards). Source code for the validator is also available.

HTML Tidy is not just a HTML validator for your web documents. It is able to correct (repair and fix) bad HTML code and give you pointers to areas where you need to change in order to make your web page accessible to people with disabilities. Source code and binaries are available for a wide variety of operating systems, including Windows 95/98/NT/2000, Mac OS, Atari, Amiga, BeOS, AIX, Linux, UnixWare, HP-UX, MSDOS, Solaris, OS/2, FreeBSD, RISC OS, MiNT (Atari) OS, etc. There is even a Java port of HTML Tidy.

This is an online version of the HTML Tidy validator that you can use to clean up your web pages if you're too lazy to download your own copy. (To get your own copy, see elsewhere on this page - listed under "HTML Tidy".)

The Web Page Purifier allows you to check your HTML pages for compliance ("purity") with various HTML standards (eg HTML 4.0 Transitional, HTML 4.0 Strict, WebTV 1.1, HTML 3.2, etc). There's a form where you can enter the URL of the page to check, or you can also download the Perl CGI source code.

If you need to check your web pages to see if they are compatible with browsers that lack certain features, this page checker might be useful. You actually have to specify which features you do not want on a page, like tables, images, etc. It is probably not as useful as the title of the site sounds, since if you knew which features you needed to avoid, you would not put them in a page in the first place. (It would be better if there were simple options where you could simply select the browser versions you want to check compatibility with, instead of having to specify features.)

Free Web Page Accessibility Checkers

This browser toolbar allows you to check your page for accessibility issues. It requires you to have IE 5 or above on Windows.

Cynthia checks your site against the US Section 508 standards and the Web Content Acessibility Guidelines (WCAG). It only allows you to test one page at a time.

A-Prompt is a Windows program that checks your pages for accessibility issues and fixes the pages for you (with your help). It has a Wizard-like interface which guides you through the individual (potential) problems that your web page may have and prompts you for information for repairing the page.

Bobby checks your HTML pages for areas that might pose difficulties for people with disabilities. You simply enter the URL of your web page and it will give you a report after it visits that URL. It can check your site against the US Section 508 Guidelines, or against the Web Content Accessibility Guidelines 1.0.

Free Cascading Style Sheets (CSS) Validators

This is the W3 Consortium's CSS validator for validating Cascading Style Sheets. You can either download it and use it on your own machine, upload your cascading style sheet (CSS) to their online service, or supply your URL for their spider to visit your site. The W3 Consortium is responsible for the various CSS and HTML standards.

This is a validator for Cascading Style Sheets (CSS) that also looks into a few browser compatibility issues with your style sheet.

Free Broken Links Validators

Worried about broken links in your web documents? This online validator from the W3 Consortium is able to recursively check your document for dead links. You simply enter a URL in the form provided, and it will visit your site and check the links.

Xenu is a utility for Windows that checks your web site for broken links. It can work both with a "live" website as well as on a copy of your web site residing on your own hard disk. It's a favourite of many webmasters for checking broken links on their site.

Free ODBC Drivers, SQL Servers and Tools, Database Libraries and Source Code

Looking for ODBC drivers? SQL Servers? SQL Tools? Source code for database libraries? Relational database management systems? ISAM (index sequential access method) libraries? Btrees? B+trees? This page contains numerous free drivers, servers, tools, libraries, source code, entire RDBMSes, etc.

If you are looking for books from which to learn SQL, one frequently recommended book on SQL is The Practical SQL Handbook: Using Structured Query Language (publisher: Addison-Wesley).

Free ODBC Drivers, SQL Servers and Tools, Database Libraries and Source Code

HSQLDB is a Java SQL relational database engine. It has a JDBC driver and supports a subset of ANSI-92 SQL with SQL 99 and 2003 enhancements. It supports both in-memory and disk-based tables, and embedded and server modes.

Sybase ASE Express Edition for Linux has all the features of Sybase's commercial offering except that it is limited to 1 CPU, 5 GB of storage and 2 GB of RAM (according to their press release). You have to register before you are allowed to download.

IBM Cloudscape is an open source Java RDBMS with a small footprint that can be embedded in Java programs. It runs on a Java virtual machine, which means that it is theoretically portable to systems that have a JVM, including AIX, Linux, Windows 2000/XP/2003, Mac OS, Mac OS X, Solaris, and OS/400.

Computer Associates' Ingres is now an open source (CA Trusted Open Source License) relational database that runs on Linux, UNIX, Windows and OpenVMS.

Berkeley DB is an embedded database system that is thread-safe, has support for arbitrary data types, allows both keyed and sequential access to records, supports cursors, logical joins, secondary indices, memory-mapped and read-only databases, architecture-independent databases, databases up to 256 terabytes (with keys and values up to 4 gigabytes), supports concurrent accesses, fine-grained locking, group commit, load balancing, transparent failover, hot backups, etc. The licence requires you to distribute the source code for any application that uses Berkeley DB when you distribute it.

SQLite is a C library with an embeddable SQL database engine. It implements most of SQL92, stores the entire database in a single file, supports databases up to 2 terabytes in size, has bindings for many programming languages (download separately), supports ACID (atomic, consistent, isolated, durable) transactions, etc. Sources for the library is available and is in the public domain.

OTL is a C++ template library. It is a wrapper around the Oracle, ODBC and DB2-CLI database APIs. When you use the library, it is expanded into direct database API function calls. The code is ANSI C++ compliant, and is integrated with the Standard Template Library (STL). OTL supports Oracle 7, Oracle 8, Oracle 8i, Oracle 9i, DB2, ODBC 3.0 and ODBC 2.5 compliant sources in Windows and Unix (such as Oracle, MS SQL Server, Sybase, MySQL, DB2, Interbase, PostgreSQL, etc).

MySQL++ is a C++ API that you can use for making MySQL queries. The software is licensed under the GNU LGPL. Precompiled binaries are available for Linux, Windows, Mac OS X, etc.

B-Tree Filer is a library of database routines (probably using b-trees as its name implies) for either MSDOS or Windows. Written in Object Pascal, it may be used in Turbo Pascal or Delphi programs.

The TurboPower FlashFiler is a free client/server database engine that supports SQL queries, huge tables, huge BLOB (binary large objects) support (up to 2GB), concurrent transactions, server plug-ins, server monitors and extenders, login security, encrypted tables, timeout handling, etc. It is a multi-threaded server that can handle multiple requests from many clients simultaneously. You can also run it as a Windows service under Windows NT/2000. TurboPower's libraries and components work with Borland Delphi and C++ Builder.

This is the Interbase 6 and Firebird ODBC driver. It aims to conform to the ODBC 3.X API CORE. It currently only runs on Win32, although plans appear to be underway to support Linux. You may use the driver free in both personal and commercial software. Source code is available under the GNU LGPL.

FirebirdSQL is an open source relational database based on the Interbase 6 engine. It runs on Linux, Windows, and a number of Unix systems.

The Microsoft SQL Server 2000 Desktop Engine, or MSDE 2000, is the free version of Microsoft's SQL Server. According to the website, it looks like you can redistribute MSDE 2000 royalty-free, although you should read their licence agreement yourself to verify this. It is designed to run on Windows 98, ME, NT Workstation, 2000 Professional.

The iODBC driver manager supports ODBC 3.X API. It is an open source release that is portable to all major Unix platforms, including Solaris, HP-UX, AIX, SCO OpenServer, SCO Unixware, SGI IRIX (Mips ABI), Digital Unix, DG-UX, Dynix/PTX, BSDI, FreeBSD and of course Linux.

This C++ library makes ODBC record sets look like an STL container. You can move through it using standard STL iterators. The author informs me that the library is free and licenced under the same terms as the SGI STL.

This is a collection of C/C++ libraries that purportedly "simplifies complex time-consuming database, socket, multithreaded programming tasks". It supports the Windows and Unix platforms.

The UnixODBC Project provides developers with a free ODBC kit distributed with source code under GNU GPL and LGPL (the LGPL applies to the library source code so that presumably you can build commercial applications with them without releasing your source code if you want). As is obvious from its name, it is designed for Unix systems, and includes ODBC sample drivers, a ODBC driver manager, a GUI administrative tool (for KDE), a data source explorer, etc. It looks like Linux is the primary platform that is supported, although there are ports for FreeBSD as well.

XDB (formerly Xbase) is "a collection of specifications, programs, utilities and a C++ class library for manipulating Xbase type datafiles and indices." That is, if you deal with dBase compatible files, such as those produced by dBase, Clipper, FoxPro, etc, this might be the library for you. It supports the DBF files, dBase's NDX index files, Clipper's NTX files, DBT memo files, and possibly others.

Libsqlora8 is a C library that hides much of the complexity of accessing Oracle databases, allowing you to use a more simplified interface. The library is provided in source code form. It works on Linux; I am not sure if other operating systems are also supported.

GQL is a C++ library that provides an abstraction of an SQL database. It provides you with a portable API that you can use with most SQL databases. A wrapper for Python is currently also in the works.

If you are looking for a free ODBC library, you might want to take a look at Libodbc++. This C++ class library provides a convenient means for you to access SQL databases. It supports a subset of JDBC 2.0, and it is distributed under the GNU LGPL.

NoSQL, a GNU GPLed relational database management system, is, as its name suggests, is not an SQL database. It's actually a shell-level tool that creates regular ASCII files that can be manipulated by other text tools (like text editors, etc). It is closely integrated with Unix, and the author created it because he wanted something he could use for simple database management tasks that didn't require the full feature set usually present in other DBMSes.

Dx is a C/C++ Linux and FreeBSD database that you can embed in your applications. It uses an extensible hashing algorithm for indexing, much like DBM, NDBM and GDBM, and can support databases spread over multiple file systems. Among its other features are flexible methods of storing and retrieving data, a sophisticated data editing facility, a small memory footprint, etc.

mSQL, or mini SQL, is a database engine that offers a subset of the ANSI SQL language. There are versions for various flavours of Unix as well as a port to Win32. The program is free for certain people (such as full-time students) and organisations (such as educational institutions, etc). A number of tools for the engine, as well as an ODBC driver, are also available A book on this server is also available: The Official Guide to Mini SQL 2.0 . It was written by the author. Another book on mSQL is MySQL and mSQL from O'Reilly's Nutshell series.

mySQL is a SQL database server which has been ported to a number of operating systems, including Linux and Win32. An ODBC driver for the server is also available. mySQL is free unless you are selling a product that includes the mySQL server. If you are looking for a book on programming this database, I read of a number of recommendations from users about Paul Dubois' MySQL . (I've not read it myself though). Another book on mySQL is MySQL and mSQL from O'Reilly's Nutshell series.

This is DBMS library cum SQL server that supports the full ANSI/ISO SQL 1992 Standard. You can access the database directly (via its DLLs) or via ODBC. The system is free for both personal and commercial use. Source code is available under a maintainence contract. You cannot however redistribute the DLL but you can always direct your customers to the website. Incredibly, the DLL is only about 600k for the full DBMS support!

According to its web site, the GNU SQL Server is a free relational database management system that supports the full SQL89 language and some of the SQL92 extensions. Like all things GNU, source code is included and protected under the GNU General Public License. You will need to check its documentation to find out what OSes are supported.

According to its website, "PostgreSQL is a sophisticated Object-Relational DBMS supporting almost all SQL constructs." It has a long history, dating back to its original incarnation as Ingres, then Postgres, and later Postgres95. An ODBC driver supporting the core functionality as well as portions of level 1 and 2 is available. Windows NT/95 is supported only on the client side, while numerous Unices and Unix-clones are fully supported.

A relational database management system that comes with full C source code, released under the GNU GPL. According to its website, it is as powerful as the complex offerings from Sybase, Oracle and IBM, but was originally written as an educational tool. It's query language is a full implementation of relational algebra. It supports Windows 95/NT, Linux, Solaris, SunOS, HP/UX, AIX, etc.

A C++ database library that is apparently free for non-commercial purposes. It supports a number of systems including various Unices, OS/2, DOS and Windows.

Free File Comparison Utilities

The tools on this page allow you to compare the differences between two files (like the well-known diff utility found on Unix systems). Some of these tools are GUI based, and will display the differences side by side in a Window, or perhaps even highlight the difference. Others are command line based (like diff). Some tools only support text files while others may be able to compare binary files.

Free File Comparison Utilities (diff tools)

P4WinMerge compares two versions of a file to the original file and produces a merged file. The GUI shows how the merge was performed, and allows you to construct a different merge file using a point and click interface. It includes synchronized scrolling that makes it easier to compare three different files, colour-coded text, re-selection and re-editing of merged changes, etc. The program runs on Windows XP, 2000, NT, and 95/98.

ExamDiff shows you the difference between two ASCII text files (Unicode not supported) by displaying the two files side by side with the changes in different colours. You can configure the colours used.

xdelta allows you to make binary diffs of two binary files. Actually, xdelta is apparently more than that - it is, according to their web page, "a complete system for managing delta-compressed storage and network transport".

This is a Java version of xdelta, a program that can make binary diffs of two files.

Need to compare two text files and get a report of which lines have changed? The GNU diff utilities can show you the changes, the context surrounding the change, etc. While a standard part of Unix system, the diff utilities are useful for operating systems that do not come with a useful file or text comparison utility. Note that the utilities are command-line based and come with full source code. If you need an MSDOS or Windows 95/98/ME port of diff, check out the DJGPP system, listed on the Free C/C++ Compilers page. I'm not sure, but I suspect the Cygwin compiler system also includes diff for Windows systems (also listed on the Free C/C++ Compilers page).

WinMerge is a Windows file differencing and merging tool. It has a Windows frontend over the GNU diff and merge utilities. It includes Visual SourceSafe integration, visual differencing of text files, the ability to diff entire directories, multiple level undos, an integrated editor,

xxdiff is a graphical file and directory comparison and merging tool. You can compare two or three files with the differences highlighted. You can also compare two directories (useful if you are trying to synchronise two directories/disks). It also has the ability to merge files, unmerge CVS conflicts into two separate files so that you can resolve the conflicts, etc. It uses an external diff program that is compatible with GNU diff (presumably in its interface). xxdiff is released under the GNU GPL and runs on IRIX, Linux, HP/UX, and DEC Tru64.

KDiff3 compares two or three text files and shows the differences between them line by line and even character by character. It also has a merge capability, an integrated editor and the ability to diff/merge directories as well. KDiff3 works on Unix systems like Linux as well as Windows.

CSDiff allows you to compare folders (directories) as well as ASCII text files, Microsoft Word files and RTF files.