<title>Most Widely Deployed SQL Database Engine</title>
<tcl>hd_keywords {most widely deployed} {most used} {most widely used}</tcl>

<h2>Most Widely Deployed and Used Database Engine</h2>

<p>SQLite is likely used more than all other database engines
combined.  Billions and billions of copies
of SQLite exist in the wild.  SQLite is found in:

<ul>
<li>Every Android device
<li>Every iPhone and iOS device
<li>Every Mac
<li>Every Windows10 machine
<li>Every Firefox, Chrome, and Safari web browser
<li>Every instance of Skype
<li>Every instance of iTunes
<li>Every Dropbox client
<li>Every TurboTax and QuickBooks
<li>PHP and Python
<li>Most television sets and set-top cable boxes
<li>Most automotive multimedia systems
<li>Countless millions of other applications
</ul>

<p>Since SQLite is used extensively in every smartphone, and there are
roughly 3.5 billion (3.5e9) smartphones in active use, each holding hundreds of
SQLite database files, it is seems likely that there are over one trillion
(1e12) SQLite databases in active use.

<h2>Most Widely Deployed Software Module of Any Type?</h2>

<p>SQLite is probably one of the top five most deployed
software modules of any description.  
Other libraries with similar reach include:

<ul>
<li>
The original <a href="http://zlib.net">zlib</a> implementation by
Jean-loup Gailly and Mark Adler.
<li>
The original reference implementation for
<a href="http://www.libpng.org">libpng</a>
<li>
Libjpeg from the <a href="http://ijg.org">Independent JPEG Group</a>
</ul>

<p>
Libc is omitted from the above list even though
it is more common than SQLite because
libc is not a single software component but rather several
competing implementations (ex: BSD vs. GNU) with similar interfaces.
There are also independent implementations of libjpeg and libpng,
though in those cases the canonical implementations are very popular.
</p>

<p>
Precise numbers are difficult to obtain and so exact rankings
are impossible.  But our best guess is that SQLite is the second
mostly widely deployed software library, after libz.
Some commentators observe that SQLite tends
to be statically linked and thus have multiple instances on
each machine, whereas libz tends to have just
a single instance per machine in the form of a shared library or DLL.
So even though the number of devices containing libz
may be greater than the number of
devices that contain SQLite, the total number of instances per device
<em>might</em> be higher for SQLite and so SQLite <em>might</em>
be the single most widely deployed and used software component.
</p>
