Numeric types are supported with the following libraries:

integer.s7i		Integer support library.
bigint.s7i		Unlimited precision integer support library.
rational.s7i		Rational number support library.
bigrat.s7i		Big rational number support library.
float.s7i		Floating point support library.
complex.s7i		Complex support library.
math.s7i		Mathematical functions and constants.

The characters in a string use the UTF-32 encoding. Strings are not '\0;' terminated. Therefore they can also contain binary data. Strings are supported with the following libraries:

string.s7i		String library with support for concatenation, indexing, slicing, comparison, changing the case, searching and replacing.
scanstri.s7i		String scanner functions to scan integer, character and string literals as well as names, and comments.
charsets.s7i		Code pages for various character sets.
unicode.s7i		Functions to convert to and from UTF-16BE, UTF-16LE, UTF-8 and UTF-7.
encoding.s7i		Encoding and decoding functions for Base64 encoding, Quoted-printable encoding, uuencoding, percent-encoding, URL encoding, Ascii85 encoding, AsciiHex encoding and Base58 encoding.

File support uses the interface types file and text together with various types to implement them. Libraries, which support standard I/O and enable I/O for various types, are also present. Files are supported with the following libraries:

file.s7i		Interface type describing sequential files.
null_file.s7i		Base implementation type for all files.
external_file.s7i		File implementation type describing OS files.
stdio.s7i		Standard input and output via files.
enable_io.s7i		Templates to enable file I/O for a given type.
keybd.s7i		Read from keyboard without buffering and echo.
editline.s7i		Filter file for linewise editing with history.
line.s7i		Filter file which reads the input linewise. Writing to a line file buffers lines and writes them to the base file with the next writeln or flush.
echo.s7i		Filter file which generates an echo of the input.
utf8.s7i		File implementation type for UTF-8 files.
utf16.s7i		File implementation type for UTF-16 files.
strifile.s7i		Implementation type for files stored in a string.
more.s7i		File implementation type to show another file screenwise.
socket.s7i		File implementation type for OS sockets.
dir.s7i		Implementation type to read directorys as files.
text.s7i		Interface type for line/column oriented files.
console.s7i		Text implementation type for text console/window.
graph_file.s7i		Implementation type to display graphic text.
window.s7i		Filter file for text windows with random access.
pixmap_file.s7i		Text implementation type to use a pixmap font.
bigfile.s7i		bigInteger versions of seek, tell and length.

Access to the operating system is supported with the following libraries:

environment.s7i		Support for program arguments, name and path of the program and environment variables.
osfiles.s7i		Functions to copy, move and remove files and functions to obtain and change file properties such as size, type, time and mode.
dir.s7i		Implementation type to read directorys as files.
getf.s7i		Read and write whole files into and from strings.
shell.s7i		Support for shell commands

There is support for sockets and TLS/SSL. Higher level protocols, such as HTTP, HTTPS, FTP and SMTP are also supported. Example programs using this features are the comanche webserver and the programs ftp7, ftpserv, tst_cli.sd7 and tst_srv.sd7. Network connections are supported with the following libraries:

sockbase.s7i		Support for socket address and primitive socket.
socket.s7i		File implementation type for sockets.
poll.s7i		Support for pollData and the poll function.
listener.s7i		Support for inet listener.
tls.s7i		Support for Transport Layer Security (TLS) and Secure Sockets Layer (SSL).
gethttp.s7i		Support to get data with the HTTP protocol.
gethttps.s7i		Support to get data with the HTTPS protocol.
ftp.s7i		Support for the FTP protocol.
smtp.s7i		Support for the SMTP protocol.
cgi.s7i		Support for the Common Gateway Interface.

The graphic libraries allow drawing, image operations, windows manipulation as well as bitmap and vector fonts. Events to redraw a window and other annoyances are managed in the graphics libraries. Graphics is used by many example programs. The mandelbr fractal viewer, the wator predator-prey simulation and the testfont bitmap and vector font demo are some of them. Graphics is supported with the following libraries:

draw.s7i		Portable graphic library.
color.s7i		Functions for color processing.
graph_file.s7i		Implementation type to display graphic text.
dialog.s7i		Dialog support library.
graph.s7i		Basic graphic library.
imagefile.s7i		Support for various image file formats (BMP, GIF, ICO, JPEG, PNG, PBM, PGM, PPM and TIFF).
bmp.s7i		Support for the BMP image file format.
gif.s7i		Support for the GIF image file format.
ico.s7i		Support for the ICO image file format.
jpeg.s7i		Support for the JPEG image file format.
png.s7i		Support for the PNG image file format.
pbm.s7i		Support for the ASCII and binary PBM image file format.
pgm.s7i		Support for the ASCII and binary PGM image file format.
ppm.s7i		Support for the ASCII and binary PPM image file format.
tiff.s7i		Support for the TIFF image file format.
font.s7i		Defines the font interface.
bitmapfont.s7i		Font implementation type for bitmap fonts.
vectorfont.s7i		Font implementation type for vector fonts.
pixmapfont.s7i		Defines pixmapFontType and the font cache.
pixmap_file.s7i		Text implementation type to use a pixmap font.

Seed7 provides a database independent API. MySQL, MariaDB, SQLLite, PostgreSQL, Oracle, Firebird, Interbase, Db2, Informix and SQL Server databases can be accessed in a portable way. Databases are supported with the following libraries:

sql_base.s7i		Base SQL access library.
db_prop.s7i		Collection of database properties.

Several methods to compress and uncompress data are provided:

gzip.s7i		Gzip uncompression function.
deflate.s7i		Deflate compression algorithm.
inflate.s7i		Inflate uncompression algorithm.
huffman.s7i		Support for Huffman coding.
lzma.s7i		Decompression with the Lempel-Ziv-Markov (LZMA) chain algorithm.
lzw.s7i		Compression and decompression with the Lempel–Ziv–Welch (LZW) algorithm.
xz.s7i		Decompression of XZ files.
zstd.s7i		Decompression of Zstandard files.
bzip2.s7i		Decompression of bzip2 files.
compress.s7i		Compression and decompression functions for PackBits of TIFF and PackBits of PDF.

Access to the contents of archive files, to operating system files and to remote files is provided with file systems. A file system can contain several files, which have a name and are situated in directories.

filesys.s7i		Defines fileSys the interface type for file systems.
osfiles.s7i		Defines osFileSys, a file system to access the local files of the operating system.
tar.s7i		Defines tarArchive, a file system to access the individual files in a tar archive.
zip.s7i		Defines zipArchive, a file system to access the individual files in a zip archive.
cpio.s7i		Defines cpioArchive, a file system to access the individual files in a cpio archive.
ar.s7i		Defines arArchive, a file system to access the individual files in an ar archive.
rpm.s7i		Defines rpmArchive, a file system to access the individual files in a rpm archive.
ftp.s7i		Defines ftpConnection, a file system to access files of a remote computer.

The following libraries do not fall in a category:

time.s7i		Time and date library.
duration.s7i		Time and date duration support library.
char.s7i		Character library.
inifile.s7i		Read key value pairs from an INI file.
propertyfile.s7i		Read key value pairs from a property-file.
htmldom.s7i		HTML dom parser.
html_ent.s7i		HTML entity handling library
html.s7i		Support functions for html
xmldom.s7i		XML dom parser.
xml_ent.s7i		XML entity handling library.
bytedata.s7i		Functions to convert byte data to and from strings.
msgdigest.s7i		Message digest and secure hash algorithms like MD4, MD5, SHA-1, SHA-224, SHA-256, SHA-384 and SHA-512.