For Users

Instructions for running, installing and configuring FIDO.

Command line usage

usage: [-h] [-v] [-q] [-recurse] [-zip] [-nocontainer] [-pronom_only]
[-input INPUT] [-filename FILENAME] [-useformats INCLUDEPUIDS]
[-nouseformats EXCLUDEPUIDS] [-matchprintf FORMATSTRING]
[-nomatchprintf FORMATSTRING] [-bufsize BUFSIZE]
[-container_bufsize CONTAINER_BUFSIZE]
[-loadformats XML1,…,XMLn] [-confdir CONFDIR]

positional arguments:
FILE files to check. If the file is -, then read content from stdin. In this case, python must be invoked with -u or it may convert the line terminators.

optional arguments:
-h, –help show this help message and exit
-v show version information
-q run (more) quietly
-recurse recurse into subdirectories
-zip recurse into zip and tar files
-nocontainer disable deep scan of container documents, increases speed but may reduce accuracy with big files
-pronom_only disables loading of format extensions file, only PRONOM signatures are loaded, may reduce accuracy of results
-input INPUT file containing a list of files to check, one per line. – means stdin
-filename FILENAME filename if file contents passed through STDIN
-useformats INCLUDEPUIDS
comma separated string of formats to use in identification
-nouseformats EXCLUDEPUIDS
comma separated string of formats not to use in identification
-matchprintf FORMATSTRING
format string (Python style) to use on match. See nomatchprintf, README.txt.
-nomatchprintf FORMATSTRING
format string (Python style) to use if no match. See README.txt
-bufsize BUFSIZE size (in bytes) of the buffer to match against (default=131072 bytes)
-container_bufsize CONTAINER_BUFSIZE
size (in bytes) of the buffer to match against (default=524288 bytes)
-loadformats XML1,…,XMLn
comma separated string of XML format files to add.
-confdir CONFDIR configuration directory to load_fido_xml, for example, the format specifications from.


(also see:

Any platform:

  1. Download the latest zip release from
  2. Unzip into some directory
  3. Open a command shell, cd to the directory that you placed the zip contents into and cd into folder ‘fido’
  4. You should now be able to see the help text:
    python -h
  5. Before identifying files with FIDO for the first time, please update signatures first
    using the ‘’ script (see below for instructions).

Updating signatures

To update FIDO with the latest PRONOM file format definitions, run:


This is an interactive CLI script which downloads the latest PRONOM signature file and signatures. Please note that it can take a while to download all PUID signatures.

If you are having trouble running the script due to firewall restrictions, see OPF wiki:

Please note that this WILL NOT update the container signature file located in the ‘conf’ folder.
The reason for this that the PRONOM container signature file contains special types
of sequences which need to be tested before FIDO can use them. If there is an update available
for the PRONOM container signature file it will show up in a next commit.


FIDO 1.0 and later will run on Python 2.7 with no other dependencies.

Format Definitions

By default, FIDO loads format information from two files conf/formats.xml
and conf/format_extensions.xml. Addition format files can be specified using
the -loadformats command line argument. They should use the same syntax as
conf/format_extensions.xml. If more than one format file needs to be specified,
then they should be comma separated as with the -formats argument.


Output is controlled with the two parameters matchprintf and nomatchprintf.
Each is a string that may contain formating information. They have access to
an object called info with the following fields:

printmatch: info.version (file format version X), info.alias (format also called X), info.apple_uti (Apple Uniform Type Identifier), info.group_size and info.group_index (if a file has multiple (tentative) hits), info.count (file N)

printnomatch: info.count (file N)

The defaults for FIDO 1.0 are:


It can be useful to provide an empty string for either, for example to ignore all failed matches, or all successful ones (see examples below).
Note that a newline needs to be added to the end of the string using \n.


FIDO returns the following matchtypes:
– fail: the object could not be identified with signature or file extension
– extension: the object could only be identified by file extension
– signature: the object has been identified with (a) PRONOM signature(s)
– container: the object has been idenfified with (a) PRONOM container signature(s)

(In some cases multiple results are returned.)

Examples running FIDO

Identify all files in the current directory and below, sending output
into file-info.csv
python -recurse . > file-info.csv

Do the same as above, but also look inside of zip or tar files:
python -recurse -zip . > file-info.csv

Take input from a list of files:
ls > files.txt
python -input files.txt
dir /b > files.txt
python -input files.txt

Take input from a pipe:
find . -type f | python -input –
dir /b | python -input –

Only show files that could not be identified.
python -matchprintf “” .

Only show files that could be identified.
python -nomatchprintf “” .

Deep scan of container objects

By default, when FIDO detects that a file is a container (compound) object,
it will start a deep (complete) scan of the file using the PRONOM container signatures.
When identifying big files, this behaviour can cause FIDO to slow down sigificantly.
You can disable deep scanning by invoking FIDO with the ‘-nocontainer’ argument.
While disabling deep scan speeds up identification, it may reduce accuracy.

At the moment (version 1.0) FIDO is not yet able to perform scanning containers which are
passed through STDIN. A workaround would be to save the stream to a temporary file and have
FIDO identify this file.