Learning CodeQL
###############

CodeQL is the code analysis platform used by security researchers to automate `variant analysis <https://semmle.com/variant-analysis>`__. 
You can use CodeQL queries to explore code and quickly find variants of security vulnerabilities and bugs. 
These queries are easy to write and share–visit the topics below and `our open source repository on GitHub <https://github.com/Semmle/ql>`__ to learn more. 
You can also try out CodeQL in the `query console <https://lgtm.com/query>`__ on `LGTM.com <https://lgtm.com>`__. 
Here, you can query open source projects directly, without having to download CodeQL databases and libraries. 

CodeQL is based on a powerful query language called QL. The following topics help you understand QL in general, as well as how to use it when analyzing code with CodeQL.

.. pull-quote::

   Important 

   If you've previously used QL, you may notice slight changes in terms we use to describe some important concepts. For more information, see our note about :doc:`Recent terminology changes <terminology-note>`.

.. toctree::
   :hidden:

   terminology-note
   

.. _getting-started:

Getting started
***************

If you are new to QL, start by looking at the following topics:

.. toctree::
   :maxdepth: 1

   introduction-to-ql
   about-ql
   beginner/ql-tutorials
   ql-etudes/river-crossing

CodeQL training and variant analysis examples
*********************************************

To start learning how to use CodeQL for variant analysis for code written in a specific language, see:

.. toctree::
   :maxdepth: -1

   ql-training

.. _writing-ql-queries:

Writing CodeQL queries
**********************

To learn more about writing your own queries, see:

.. toctree::
   :maxdepth: 3
   :includehidden:

   writing-queries/writing-queries

For more information on using CodeQL to query code written in a specific language, see:

.. toctree::
   :maxdepth: 2
   :includehidden:

   cpp/ql-for-cpp
   csharp/ql-for-csharp
   cobol/ql-for-cobol
   go/ql-for-go
   java/ql-for-java
   javascript/ql-for-javascript
   python/ql-for-python

Advanced QL and technical information
*************************************

For more technical information see:

.. toctree::
   :maxdepth: 2
   :includehidden:

   advanced/advanced-ql
   technical-info    

Reference topics
****************

For a more comprehensive guide to the query language itself, see the following reference topics: 

- `QL language handbook <https://help.semmle.com/QL/ql-handbook/index.html>`__—a description of important concepts in QL.
- `QL language specification <https://help.semmle.com/QL/ql-spec/language.html>`__—a formal specification of QL.

Search
******

.. * :ref:`genindex` remove index for the time being as we currently have no tags

* :ref:`search`