diff --git a/.idea/csv-plugin.xml b/.idea/csv-plugin.xml
index c1db85f..fcbe183 100644
--- a/.idea/csv-plugin.xml
+++ b/.idea/csv-plugin.xml
@@ -3,6 +3,13 @@
   <component name="CsvFileAttributes">
     <option name="attributeMap">
       <map>
+        <entry key="/src/inspectors.rs">
+          <value>
+            <Attribute>
+              <option name="separator" value="&#9;" />
+            </Attribute>
+          </value>
+        </entry>
         <entry key="/src/main.rs">
           <value>
             <Attribute>
diff --git a/src/extensionset.rs b/src/extensionset.rs
index 47667fe..7583296 100644
--- a/src/extensionset.rs
+++ b/src/extensionset.rs
@@ -1,32 +1,42 @@
+//! Sets of extensions for use with [Parameter](crate::parameters::Parameters)'s `-E` flag.
 use clap::Clap;
 
 #[derive(Clap, PartialEq, Debug)]
 pub enum ExtensionSet {
+	/// Extensions used for image file formats, such as `png`, `jpeg`, `webp`, etc.
 	Images,
+	/// Extensions used for audio file formats, such as `mp3`, `ogg`, `flac`, etc.
 	Audio,
+	/// Extensions used for video file formats, such as `mkv`, `mp4`, `mov`, etc.
 	Videos,
+	/// Extensions used for media file formats. This acts as a combination of the [Images](ExtensionSet::Images),
+	/// [Audio](ExtensionSet::Audio) and [Videos](ExtensionSet::Videos) variants.
 	Media,
+	/// Extensions used for document file formats, such as `pdf`, `odt`, `docx`, etc.
 	Documents,
+	/// Extensions used for archive file formats, such as `zip`, `zst`, `gz`, etc.
 	Archives,
 }
 
 impl ExtensionSet {
+	/// The list of known extensions for this ExtensionSet.
 	pub fn extensions(&self) -> Vec<&str> {
 		match self {
-			Self::Images => mime_guess::get_mime_extensions_str("image/*"),
-			Self::Videos => mime_guess::get_mime_extensions_str("video/*"),
-			Self::Audio => mime_guess::get_mime_extensions_str("audio/*"),
-			Self::Documents => Some(
-				&[
-					"pdf", "doc", "docx", "ppt", "pptx", "xls", "xlsx", "csv", "tsv", "odt", "ods", "odp", "oda", "rtf", "ps",
-				][..],
-			),
+			Self::Images => mime_guess::get_mime_extensions_str("image/*").unwrap().to_vec(),
+			Self::Audio => mime_guess::get_mime_extensions_str("audio/*").unwrap().to_vec(),
+			Self::Videos => mime_guess::get_mime_extensions_str("video/*").unwrap().to_vec(),
+			Self::Media => [
+				Self::Images.extensions(),
+				Self::Audio.extensions(),
+				Self::Videos.extensions(),
+			]
+			.concat(),
+			Self::Documents => vec![
+				"pdf", "doc", "docx", "ppt", "pptx", "xls", "xlsx", "csv", "tsv", "odt", "ods", "odp", "oda", "rtf", "ps",
+			],
 			// many compressed file types follow the name scheme "application/x.+compressed.*" - maybe this can be used
 			// somehow to extract extensions for compressed files from mime_guess?
-			Self::Archives => Some(&["zip", "tar", "gz", "zst", "xz", "rar", "7z", "bz", "bz2"][..]),
-			_ => todo!(),
+			Self::Archives => vec!["zip", "tar", "gz", "zst", "xz", "rar", "7z", "bz", "bz2"],
 		}
-		.unwrap()
-		.to_vec()
 	}
 }
diff --git a/src/findings.rs b/src/findings.rs
index e4c11a5..2fbbee1 100644
--- a/src/findings.rs
+++ b/src/findings.rs
@@ -5,9 +5,13 @@ use smartstring::alias::String;
 
 use crate::inspectors::mime_extension_lookup;
 
+/// Information about a scanned file.
 pub struct Findings {
+	/// The location of the scanned file.
 	pub file: PathBuf, // TODO: replace with Path???? <'a> and all that
+	/// Whether or not the file's extension is valid for its mimetype.
 	pub valid: bool,
+	/// The file's mimetype.
 	pub mime: Mime,
 }
 
diff --git a/src/formats.rs b/src/formats.rs
index a6668f6..bc598ff 100644
--- a/src/formats.rs
+++ b/src/formats.rs
@@ -1,3 +1,5 @@
+//! The various formats that [fif](crate) can output to.
+
 use std::io::{self, Write};
 #[cfg(unix)]
 use std::os::unix::ffi::OsStrExt;
@@ -8,8 +10,10 @@ use snailquote::escape;
 use crate::scanerror::ScanError;
 use crate::{Findings, BACKEND};
 
+/// The current version of fif, as defined in Cargo.toml.
 const VERSION: Option<&'static str> = option_env!("CARGO_PKG_VERSION");
 
+#[doc(hidden)]
 type Entries = [Result<Findings, (ScanError, PathBuf)>];
 
 enum Writable<'a> {
@@ -48,7 +52,7 @@ fn smart_write<W: Write>(f: &mut W, writeables: &[Writable]) -> io::Result<()> {
 					f.write_all(&*path.as_os_str().as_bytes())?;
 					#[cfg(windows)]
 					write!(f, "{}", path.as_os_str().to_string_lossy())?; // TODO: implement bonked strings for windows
-					// f.write_all(&*path.as_os_str().encode_wide().collect::<Vec<u16>>())?;
+																											// f.write_all(&*path.as_os_str().encode_wide().collect::<Vec<u16>>())?;
 					write!(f, "'''")?
 				}
 			}
@@ -97,6 +101,7 @@ pub trait Format {
 }
 
 // TODO: maybe make a batch script version for windows
+/// Bourne-Shell compatible script.
 pub struct Script {}
 
 impl Format for Script {
diff --git a/src/inspectors.rs b/src/inspectors.rs
index e3855e5..c359a29 100644
--- a/src/inspectors.rs
+++ b/src/inspectors.rs
@@ -1,3 +1,5 @@
+//! Functions for getting the mime type and extension of a file.
+
 use std::fs::File;
 use std::io;
 use std::io::{Read, Seek, SeekFrom};
@@ -10,13 +12,17 @@ use smartstring::alias::String;
 
 use crate::mimedb::MimeDb;
 
-// rather than reading once into a large buffer, it tends to be faster to first try identifying the file from a small
-// chunk read from the top, and *then* proceeding with the large buffer. many file formats can be easily identified by
-// the first 128 bytes. of course, not all formats can, and some (OOXML...) require reading a long ways in.
-
+/// The number of bytes to read initially.
+///
+/// Rather than reading the entire file all at once into a [BUF_SIZE] buffer, it tends to be faster to read a small
+/// chunk of the file and trying to identify that, proceeding with the larger buffer if that fails. Many file formats
+/// can be identified with the first few dozen bytes, so the "happy path" will likely be taken in the majority of cases.
 const INITIAL_BUF_SIZE: usize = 128;
+
+/// The number of bytes to read if the file couldn't be identified from its first [INITIAL_BUF_SIZE] bytes.
 const BUF_SIZE: usize = 4096;
 
+/// Tries to identify the mimetype of a file from a given path.
 pub fn mime_type<T: MimeDb>(db: &T, path: &Path) -> io::Result<Option<Mime>> {
 	let mut buffer = [0; INITIAL_BUF_SIZE];
 	let mut file = File::open(path)?;
@@ -59,6 +65,10 @@ cached! {
 	MIMEXT;
 	fn mime_extension_lookup(mime: Mime) -> Option<Vec<String>> = {
 
+		// Returns a list of known extensions for this mime type, if any.
+		// ↑ this is supposed to be a doc comment, but the cached! macro doesn't support that... maybe i should switch to
+		// the derive macro
+
 		// match on the mime's `essence_str` rather than the mime itself - mime_guess::get_mime_extensions ignores the type
 		// suffix, treating "image/svg+xml" as "image/svg", and thus fails to find any extensions. passing the essence_str
 		// (which includes the suffix) fixes this.
diff --git a/src/main.rs b/src/main.rs
index fa1f044..dd68a62 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -31,8 +31,8 @@ use crate::formats::{Format, Script};
 use crate::mimedb::MimeDb;
 use crate::parameters::OutputFormat;
 use crate::scanerror::ScanError;
-use std::process::exit;
 use env_logger::Env;
+use std::process::exit;
 
 mod extensionset;
 mod findings;
@@ -44,23 +44,27 @@ mod scanerror;
 
 #[cfg(test)]
 mod tests;
+mod util;
 
 cfg_if! {
 	if #[cfg(any(all(not(unix), not(feature = "xdg-mime-backend")), all(unix, feature = "infer-backend")))] {
+		/// A [OnceCell] holding an instance of [mimedb::MimeDb].
 		static MIMEDB: OnceCell<mimedb::InferDb> = OnceCell::new();
+		/// The backend being used; either "Infer" or "XDG-Mime".
 		const BACKEND: &str = "Infer";
 	} else {
+		/// A [OnceCell] holding an instance of [mimedb::MimeDb].
 		static MIMEDB: OnceCell<mimedb::XdgDb> = OnceCell::new();
+		/// The backend being used; either "Infer" or "XDG-Mime".
 		const BACKEND: &str = "XDG-Mime";
 	}
 }
 
+#[doc(hidden)]
 fn main() {
 	let args: parameters::Parameters = parameters::Parameters::parse();
 
-	let mut builder = env_logger::Builder::from_env(
-		Env::new().filter_or("RUST_LOG", "INFO")
-	);
+	let mut builder = env_logger::Builder::from_env(Env::new().filter_or("RUST_LOG", "INFO"));
 
 	builder
 		// .format(|buf, r| writeln!(buf, "{} - {}", r.level(), r.args()))
@@ -138,6 +142,7 @@ fn main() {
 
 cfg_if! {
 	if #[cfg(windows)] {
+		/// Determines whether or not a file is hidden by checking its win32 file attributes.
 		fn is_hidden(entry: &DirEntry) -> bool {
 		use std::os::windows::prelude::*;
 		std::fs::metadata(entry.path()) // try to get metadata for file
@@ -147,6 +152,7 @@ cfg_if! {
 			)
 		}
 	} else {
+		/// Determines whether or not a file is hidden by checking for a leading full stop.
 		fn is_hidden(entry: &DirEntry) -> bool {
 		entry
 			.file_name()
@@ -156,6 +162,7 @@ cfg_if! {
 	}
 }
 
+/// Returns `true` if a file matches the given criteria.
 fn wanted_file(scan_hidden: bool, exts: &[&str], entry: &DirEntry) -> bool {
 	if !scan_hidden && is_hidden(entry) {
 		// skip hidden files and directories. this check is performed first because it's very lightweight.
@@ -176,11 +183,20 @@ fn wanted_file(scan_hidden: bool, exts: &[&str], entry: &DirEntry) -> bool {
 	exts.contains(&ext.unwrap().to_lowercase().as_str())
 }
 
+/// Given a file path, returns its extension, using [std::path::Path::extension].
+///
+/// The extension is currently [converted to a lossy string](std::ffi::OsStr::to_string_lossy), although it will
+/// (eventually) in future return an OsStr instead.
 fn extension_from_path(path: &Path) -> Option<String> {
 	path.extension(). // Get the path's extension
 		map(|e| String::from(e.to_string_lossy())) // Convert from OsStr to String
 }
 
+/// Inspects the given entry, returning a [Findings] on success and a tuple of [ScanError] and [PathBuf] on failure.
+///
+/// In the event of an IO error, the returned ScanError will be of type [ScanError::File]. Otherwise, a
+/// [ScanError::Mime] will be returned, meaning that the file was scanned successfully, but a mimetype could not be
+/// determined.
 fn scan_file(entry: &DirEntry) -> Result<Findings, (ScanError, PathBuf)> {
 	// try to determine mimetype for this entry
 	let result = inspectors::mime_type(MIMEDB.get().unwrap(), entry.path());
@@ -219,6 +235,7 @@ fn scan_file(entry: &DirEntry) -> Result<Findings, (ScanError, PathBuf)> {
 	})
 }
 
+/// Takes a slice of [DirEntry]s and calls [scan_file] on each one, returning the results in a vector.
 fn scan_from_walkdir(entries: &[DirEntry]) -> Vec<Result<Findings, (ScanError, PathBuf)>> {
 	cfg_if! {
 		if #[cfg(feature = "multi-threaded")] {
@@ -240,6 +257,8 @@ fn scan_from_walkdir(entries: &[DirEntry]) -> Vec<Result<Findings, (ScanError, P
 	}
 }
 
+/// Scans a given directory with [WalkDir], filters with [wanted_file], checks for errors, and returns a vector of
+/// [DirEntry]s.
 fn scan_directory(dirs: &PathBuf, exts: &Vec<&str>, scan_hidden: bool) -> Option<Vec<DirEntry>> {
 	let stepper = WalkDir::new(dirs).into_iter();
 	let mut probably_fatal_error = false;
@@ -278,6 +297,7 @@ fn scan_directory(dirs: &PathBuf, exts: &Vec<&str>, scan_hidden: bool) -> Option
 	}
 }
 
+/// Initialises [MIMEDB] with a value dependent on the current backend.
 fn init_db() {
 	cfg_if! {
 		if #[cfg(any(all(not(unix), not(feature = "xdg-mime-backend")), all(unix, feature = "infer-backend")))] {
diff --git a/src/mimedb.rs b/src/mimedb.rs
index 9be3820..43bb6db 100644
--- a/src/mimedb.rs
+++ b/src/mimedb.rs
@@ -1,3 +1,5 @@
+//! Backend-neutral Mime database implementation.
+
 use cfg_if::cfg_if;
 use mime_guess::Mime;
 
diff --git a/src/parameters.rs b/src/parameters.rs
index 5f893bf..750029b 100644
--- a/src/parameters.rs
+++ b/src/parameters.rs
@@ -1,3 +1,5 @@
+//! [Clap] struct used to parse command line arguments.
+
 use std::path::PathBuf;
 
 use crate::extensionset::ExtensionSet;
@@ -10,6 +12,8 @@ pub enum OutputFormat {
 	Text,
 }
 
+// TODO: convert this to macro style: https://docs.rs/clap/3.0.0-beta.2/clap/index.html#using-macros
+
 #[derive(Clap, Debug)]
 #[clap(version = option_env!("CARGO_PKG_VERSION").unwrap_or("???"))]
 pub struct Parameters {
@@ -54,4 +58,4 @@ impl Parameters {
 			unreachable!()
 		}
 	}
-}
\ No newline at end of file
+}
diff --git a/src/scanerror.rs b/src/scanerror.rs
index df8d710..6b2052f 100644
--- a/src/scanerror.rs
+++ b/src/scanerror.rs
@@ -2,7 +2,9 @@ use std::fmt::{Display, Formatter, Result};
 
 #[derive(Debug)]
 pub enum ScanError {
+	/// Something went wrong while trying to read the given file.
 	File,
+	/// Failed to determine the mimetype of the given file.
 	Mime,
 }
 
diff --git a/src/tests/mod.rs b/src/tests/mod.rs
index d78f9e5..0a331b8 100644
--- a/src/tests/mod.rs
+++ b/src/tests/mod.rs
@@ -2,13 +2,13 @@ use crate::inspectors::mime_extension_lookup;
 use crate::mimedb::*;
 use crate::{extension_from_path, init_db, scan_directory, scan_from_walkdir};
 
+use crate::parameters::Parameters;
 use cfg_if::cfg_if;
 use mime_guess::mime::{APPLICATION_OCTET_STREAM, APPLICATION_PDF, IMAGE_JPEG, IMAGE_PNG};
 use mime_guess::Mime;
 use smartstring::alias::String;
 use std::collections::HashMap;
 use std::path::Path;
-use crate::parameters::Parameters;
 
 const JPEG_BYTES: &[u8] = b"\xFF\xD8\xFF";
 const PNG_BYTES: &[u8] = b"\x89\x50\x4E\x47\x0D\x0A\x1A\x0A";
@@ -118,16 +118,16 @@ fn simple_directory() {
 			// 2. ensure mime type detected is IMAGE_PNG
 			assert_eq!(result.mime, IMAGE_PNG);
 			// 3. ensure recommended extension is in the list of known extensions for PNG files
-			assert!(mime_extension_lookup(IMAGE_PNG).unwrap().contains(&result.recommended_extension().unwrap()));
+			assert!(mime_extension_lookup(IMAGE_PNG)
+				.unwrap()
+				.contains(&result.recommended_extension().unwrap()));
 			continue;
 		}
 
 		// check if the recommended extension for this file is in the list of known extensions for its mimetype
-		assert!(
-			mime_extension_lookup(result.mime.clone())
-				.unwrap()
-				.contains(&result.recommended_extension().unwrap())
-		);
+		assert!(mime_extension_lookup(result.mime.clone())
+			.unwrap()
+			.contains(&result.recommended_extension().unwrap()));
 
 		// make sure the guessed mimetype is correct based on the extension of the scanned file
 		assert_eq!(
@@ -156,4 +156,4 @@ fn argument_parsing() {
 
 	// exts should be none
 	assert!(args.exts.is_none());
-}
\ No newline at end of file
+}