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+Invalid UTF Policy
+</div>
+</div>
+
+
+
+
+
+<h1 id="garbage_in_garbage_out"><span>1. </span>Garbage In, Garbage Out</h1>
+
+<p>
+With regard to invalid UTF, SQLite follows a policy of
+Garbage-In, Garbage-Out (GIGO). If you insert invalid UTF
+into an SQLite database, then try to query that data, what you get back out
+might not be exactly what you put in.  If you put garbage in, then you
+may not complain if you get different garbage back out.
+
+</p><p>
+For the purposes of this discussion, "invalid UTF" can mean any of
+the following circumstances:
+
+</p><ul>
+<li><p>
+Invalid surrogate pairs in UTF-16.
+
+</p></li><li><p>
+Invalid multi-byte sequences in UTF-8.
+
+</p></li><li><p>
+Using more bytes of UTF-8 than necessary to represent a single
+code point.  (Example:  encoding 'A' as the two-byte sequence
+0xc1, 0x01 instead of just a single 0x41 byte.)
+
+</p></li><li><p>
+NUL characters (U+0000) embedded in strings.
+
+</p></li><li><p>
+Invalid sequences of combining characters.
+
+</p></li><li><p>
+UTF-8 or UTF-16 bytes sequences that encode numbers that are not
+defined Unicode characters.
+
+</p></li></ul>
+
+<h2 id="invalid_utf_will_never_cause_memory_errors"><span>1.1. </span>Invalid UTF will never cause memory errors</h2>
+
+<p>
+If you insert invalid UTF into an SQLite database, then SQLite makes
+no guarantees about what text you might get back out.  But it does
+promise that invalid UTF will never cause memory errors
+(array overruns, reads or writes of uninitialized memory, etc), at
+least for the built-in processing of SQLite.
+In other words, invalid UTF will not cause SQLite to crash.
+
+</p><p>
+This promise only applies to the core SQLite components, not
+application-provided extensions, of course.
+If an application adds new application-defined SQL functions or
+virtual tables or collating sequences or other extensions, and a
+database contains invalid UTF, then invalid UTF might get passed
+into those extensions.  If the invalid UTF causes one of those
+extensions to crash, then that is a problem with the extension,
+not with SQLite.
+
+</p><h1 id="no_enforcement_of_text_formatting_rules"><span>2. </span>No enforcement of text formatting rules</h1>
+
+<p>
+SQLite does not try to enforce UTF formatting rules.  You can
+insert invalid UTF into a TEXT field and SQLite will not complain
+about this.  It stores the invalid TEXT as best it can.  SQLite
+sees its role in the world as a storage engine, not a text format
+validation engine.
+
+</p><h1 id="best_effort_to_preserve_text"><span>3. </span>Best effort to preserve text</h1>
+
+<p>
+SQLite does not promise to always preserve invalid UTF, but it does
+make an effort.  Generally speaking, if you insert invalid UTF into
+SQLite, you will get the exact same byte sequence back out, as long
+as you do not ask SQLite to transform the text in any way.
+
+</p><p>
+For example, if you insert some UTF-16LE with invalid surrogates into
+a TEXT column of a table of a database that has <a href="pragma.html#pragma_encoding">PRAGMA encoding=UTF16LE</a>,
+then later query that column using <a href="c3ref/column_blob.html">sqlite3_column_text16()</a>, you will 
+probably get back the same exact invalid UTF-16.  But if you insert the
+same invalid UTF-16LE content in a <a href="pragma.html#pragma_encoding">PRAGMA encoding=UTF8</a> database,
+the content must be converted into UTF8 when it is stored, which could
+cause irreversible changes to the content.  Or if you insert that
+same invalid UTF-16LE content into a <a href="pragma.html#pragma_encoding">PRAGMA encoding=UTF16LE</a> database
+but then read it out using <a href="c3ref/column_blob.html">sqlite3_column_text()</a>, then a UTF16 to
+UTF8 conversion must occur during the read-out and that conversion might
+introduce irreversible changes.
+
+</p><p>
+Or, suppose you are doing everything using UTF-8 (the most common case).
+Invalid UTF-8 will normally pass through the database without any change
+in its byte sequence.  However, if you try to transform the invalid
+UTF-8 with SQL function like <a href="lang_corefunc.html#substr">substr()</a> or <a href="lang_corefunc.html#replace">replace()</a>
+or if you try to do string matching with the <a href="lang_expr.html#like">LIKE</a> operator, then
+you might get unexpected results.
+
+</p><p>
+So, in other words, SQLite does not actively try to subvert your
+invalid text.  But when you ask SQLite to make transformations of invalid
+UTF, there are no guarantees that those transformations will be reversible
+or even sensible.
+</p><p align="center"><small><i>This page last modified on  <a href="https://sqlite.org/docsrc/honeypot" id="mtimelink"  data-href="https://sqlite.org/docsrc/finfo/pages/invalidutf.in?m=36c2d62680437c3b4">2021-12-13 15:03:51</a> UTC </small></i></p>
+