diff --git a/gleam.toml b/gleam.toml
index e3760d9..56e3346 100644
--- a/gleam.toml
+++ b/gleam.toml
@@ -20,6 +20,7 @@ lustre_ssg = "~> 0.5.0"
 gleam_javascript = "~> 0.8"
 ranged_int = "~> 2.0"
 bigi = "~> 3.0"
+simplifile = "~> 1.7"
 
 [dev-dependencies]
 gleeunit = "~> 1.0"
diff --git a/manifest.toml b/manifest.toml
index e7340e8..c7e8c96 100644
--- a/manifest.toml
+++ b/manifest.toml
@@ -27,3 +27,4 @@ gleeunit = { version = "~> 1.0" }
 lustre = { version = "~> 4.1" }
 lustre_ssg = { version = "~> 0.5.0" }
 ranged_int = { version = "~> 2.0" }
+simplifile = { version = "~> 1.7"}
diff --git a/src/ffi_buffer.mjs b/src/ffi_buffer.mjs
deleted file mode 100644
index dd93afb..0000000
--- a/src/ffi_buffer.mjs
+++ /dev/null
@@ -1,3 +0,0 @@
-export function to_string(buffer) {
-  return buffer.toString("utf8");
-}
diff --git a/src/ffi_exceptions.mjs b/src/ffi_exceptions.mjs
deleted file mode 100644
index 1f7718f..0000000
--- a/src/ffi_exceptions.mjs
+++ /dev/null
@@ -1,9 +0,0 @@
-import { Ok, Error } from "./gleam.mjs";
-
-export function resultify(callback) {
-  try {
-    return new Ok(callback());
-  } catch (err) {
-    return new Error(err);
-  }
-}
diff --git a/src/ffi_fs.mjs b/src/ffi_fs.mjs
deleted file mode 100644
index 08c371b..0000000
--- a/src/ffi_fs.mjs
+++ /dev/null
@@ -1,5 +0,0 @@
-import { mkdirSync } from "node:fs";
-
-export function mkdirP(path) {
-  return mkdirSync(path, { recursive: true });
-}
diff --git a/src/gloss/builder.gleam b/src/gloss/builder.gleam
index eff1af8..bd59055 100644
--- a/src/gloss/builder.gleam
+++ b/src/gloss/builder.gleam
@@ -1,3 +1,6 @@
+//// The builder contains convenience functions to interface with the different
+//// parts of gloss, using the configuration to control what is done.
+
 import gleam/result
 import gloss/parser
 import gloss/rendering/database as render_database
@@ -5,24 +8,29 @@ import gloss/config.{type Configuration}
 import gloss/models/database.{type Database}
 import gloss/compiler.{type CompileDatabase}
 
+/// Something failed when building the blog.
 pub type BuildError {
   ParseError(err: parser.ParseError)
   WriteError(err: config.WriteError)
 }
 
+/// Parse the blog's input files.
 pub fn parse(config: Configuration) {
   config.parser()
   |> result.map_error(ParseError)
 }
 
+/// Compile the post and page content into HTML strings.
 pub fn compile(db: Database, config: Configuration) {
   config.compiling.database_compiler(db, config.compiling.item_compiler)
 }
 
+/// Render the content into HTML pages.
 pub fn render(db: Database, compiled: CompileDatabase, config: Configuration) {
   config.rendering.renderer(db, compiled, config)
 }
 
+/// Write the render database into files.
 pub fn write(posts: render_database.RenderDatabase, config: Configuration) {
   config.writer(posts, config)
   |> result.map_error(WriteError)
diff --git a/src/gloss/compiler.gleam b/src/gloss/compiler.gleam
index 8722fe1..80e7d25 100644
--- a/src/gloss/compiler.gleam
+++ b/src/gloss/compiler.gleam
@@ -1,3 +1,6 @@
+//// Compiling means turning post and page content into HTML. By default this
+//// content is Markdown that is compiled with Marked.js.
+
 import gleam/option
 import gleam/dict.{type Dict}
 import gleam/list
@@ -7,29 +10,36 @@ import gloss/models/page.{type Page}
 import gloss/models/database.{type Database, type PostID}
 import gloss/utils/marked
 
+/// Compiled post content: strings that contain HTML.
 pub type PostContent {
   PostContent(full: String, short: option.Option(String))
 }
 
+/// A post and its compiled content.
 pub type CompiledPost {
   CompiledPost(orig: Post, content: PostContent)
 }
 
+/// A page and its compiled content.
 pub type CompiledPage {
   CompiledPage(orig: Page, content: String)
 }
 
+/// A function to compile the given string content into an HTML string.
 pub type Compiler =
   fn(String, Database) -> String
 
+/// Structure where the compilation results are stored.
 pub type CompileDatabase {
   CompileDatabase(posts: Dict(PostID, CompiledPost), pages: List(CompiledPage))
 }
 
+/// The default compiler that uses Marked.js with default settings.
 pub fn default_compiler(content: String, _db: Database) {
   marked.default_parse(content)
 }
 
+/// Compile contents of the database using the given compiler.
 pub fn compile(db: Database, compiler: Compiler) {
   CompileDatabase(
     posts: compile_posts(db, compiler),
@@ -37,6 +47,7 @@ pub fn compile(db: Database, compiler: Compiler) {
   )
 }
 
+/// Compile all posts in the database using the given compiler.
 pub fn compile_posts(
   db: Database,
   compiler: Compiler,
@@ -59,6 +70,7 @@ pub fn compile_posts(
   dict.from_list(posts)
 }
 
+/// Compile all pages in the database using the given compiler.
 pub fn compile_pages(db: Database, compiler: Compiler) {
   database.pages(db)
   |> list.map(fn(page) {
diff --git a/src/gloss/internal/utils/meta_url.gleam b/src/gloss/internal/utils/meta_url.gleam
new file mode 100644
index 0000000..0f407cb
--- /dev/null
+++ b/src/gloss/internal/utils/meta_url.gleam
@@ -0,0 +1,2 @@
+@external(javascript, "../../../ffi_meta_url.mjs", "metaURL")
+pub fn get() -> String
diff --git a/src/gloss/utils/object.gleam b/src/gloss/internal/utils/object.gleam
similarity index 51%
rename from src/gloss/utils/object.gleam
rename to src/gloss/internal/utils/object.gleam
index 67248e3..af7eda6 100644
--- a/src/gloss/utils/object.gleam
+++ b/src/gloss/internal/utils/object.gleam
@@ -1,10 +1,10 @@
 pub type Object
 
-@external(javascript, "../../ffi_object.mjs", "create")
+@external(javascript, "../../../ffi_object.mjs", "create")
 pub fn new() -> Object
 
-@external(javascript, "../../ffi_object.mjs", "set")
+@external(javascript, "../../../ffi_object.mjs", "set")
 pub fn set(object object: Object, prop prop: String, value value: a) -> Object
 
-@external(javascript, "../../ffi_object.mjs", "get")
+@external(javascript, "../../../ffi_object.mjs", "get")
 pub fn get(object object: Object, prop prop: String) -> b
diff --git a/src/gloss/utils/path.gleam b/src/gloss/internal/utils/path.gleam
similarity index 100%
rename from src/gloss/utils/path.gleam
rename to src/gloss/internal/utils/path.gleam
diff --git a/src/gloss/parser.gleam b/src/gloss/parser.gleam
index 11776d0..1eddcf2 100644
--- a/src/gloss/parser.gleam
+++ b/src/gloss/parser.gleam
@@ -2,7 +2,7 @@ import gleam/result
 import gleam/list
 import gleam/regex
 import gleam/string
-import gloss/utils/fs
+import simplifile
 import gloss/models/database.{type Database}
 import gloss/parser/common
 import gloss/parser/post
@@ -15,7 +15,7 @@ pub type Parser =
   fn() -> Result(Database, ParseError)
 
 pub type ParseError {
-  FileError(path: String, err: fs.FSError)
+  FileError(path: String, err: simplifile.FileError)
   PostParseError(filename: String, err: common.ParseError)
   MenuParseError
 }
@@ -28,7 +28,7 @@ pub fn default_parse() -> Result(Database, ParseError) {
 
 pub fn parse_posts(db: Database, path: String) -> Result(Database, ParseError) {
   use filenames <- result.try(
-    fs.readdir(path)
+    simplifile.read_directory(path)
     |> result.map_error(fn(err) { FileError(path, err) }),
   )
 
@@ -48,7 +48,7 @@ pub fn parse_posts(db: Database, path: String) -> Result(Database, ParseError) {
     result.all(
       list.map(filenames, fn(file) {
         use contents <- result.try(
-          fs.read_file(path <> "/" <> file)
+          simplifile.read(path <> "/" <> file)
           |> result.map_error(fn(err) { FileError(file, err) }),
         )
 
@@ -63,7 +63,7 @@ pub fn parse_posts(db: Database, path: String) -> Result(Database, ParseError) {
 
 pub fn parse_pages(db: Database, path: String) -> Result(Database, ParseError) {
   use filenames <- result.try(
-    fs.readdir(path)
+    simplifile.read_directory(path)
     |> result.map_error(fn(err) { FileError(path, err) }),
   )
 
@@ -74,7 +74,7 @@ pub fn parse_pages(db: Database, path: String) -> Result(Database, ParseError) {
     })
     |> list.map(fn(file) {
       use contents <- result.try(
-        fs.read_file(path <> "/" <> file)
+        simplifile.read(path <> "/" <> file)
         |> result.map_error(fn(err) { FileError(file, err) }),
       )
 
@@ -87,10 +87,10 @@ pub fn parse_pages(db: Database, path: String) -> Result(Database, ParseError) {
 }
 
 pub fn parse_menu(db: Database, file: String) -> Result(Database, ParseError) {
-  case fs.exists(file) {
+  case simplifile.verify_is_file(file) {
     Ok(True) -> {
       use contents <- result.try(
-        fs.read_file(file)
+        simplifile.read(file)
         |> result.map_error(fn(err) { FileError(file, err) }),
       )
 
diff --git a/src/gloss/utils/buffer.gleam b/src/gloss/utils/buffer.gleam
deleted file mode 100644
index 01fd842..0000000
--- a/src/gloss/utils/buffer.gleam
+++ /dev/null
@@ -1,4 +0,0 @@
-pub type Buffer
-
-@external(javascript, "../../ffi_buffer.mjs", "to_string")
-pub fn to_string(buf buf: Buffer) -> String
diff --git a/src/gloss/utils/date.gleam b/src/gloss/utils/date.gleam
index 9df18a3..b40fdf8 100644
--- a/src/gloss/utils/date.gleam
+++ b/src/gloss/utils/date.gleam
@@ -19,14 +19,15 @@ pub type Month {
   Dec
 }
 
-/// All months in order
+/// All months in order.
 pub const months = [Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec]
 
-/// A date with 1-indexed years and days
+/// A date with 1-indexed years and days.
 pub type Date {
   Date(year: Int, month: Month, day: Day)
 }
 
+/// Parse an integer into a month.
 pub fn parse_month(month_int: Int) -> Result(Month, Nil) {
   case month_int {
     1 -> Ok(Jan)
@@ -45,6 +46,7 @@ pub fn parse_month(month_int: Int) -> Result(Month, Nil) {
   }
 }
 
+/// Get the number of days in a month in a given year.
 pub fn days_in_month(month: Month, year: Int) {
   case month {
     Jan -> 31
@@ -77,6 +79,7 @@ pub fn days_in_month(month: Month, year: Int) {
   }
 }
 
+/// Check if a given date is valid.
 pub fn is_valid_date(date: Date) -> Bool {
   let day = day.to_int(date.day)
   use <- bool.guard(day < 1, False)
@@ -97,6 +100,7 @@ pub fn compare(a: Date, b: Date) -> Order {
   }
 }
 
+/// Convert a month to a 1-indexed int.
 pub fn month_to_int(month: Month) -> Int {
   case month {
     Jan -> 1
@@ -114,6 +118,7 @@ pub fn month_to_int(month: Month) -> Int {
   }
 }
 
+/// Convert a month to an English month name string.
 pub fn month_to_string(month: Month) -> String {
   case month {
     Jan -> "January"
@@ -131,6 +136,7 @@ pub fn month_to_string(month: Month) -> String {
   }
 }
 
+/// Format a date in the format "2 Aug 2024".
 pub fn format(date: Date) -> String {
   int.to_string(day.to_int(date.day))
   <> " "
@@ -139,6 +145,7 @@ pub fn format(date: Date) -> String {
   <> int.to_string(date.year)
 }
 
+/// Format a date in the ISO 8601 format.
 pub fn format_iso(date: Date) -> String {
   int.to_string(date.year)
   <> "-"
diff --git a/src/gloss/utils/exceptions.gleam b/src/gloss/utils/exceptions.gleam
deleted file mode 100644
index 6c9d977..0000000
--- a/src/gloss/utils/exceptions.gleam
+++ /dev/null
@@ -1,10 +0,0 @@
-/// A result (of type a) from an external function that can also raise an error
-/// (of type b).
-pub type CanRaise(a, b) {
-  CanRaise(value: a, error: b)
-}
-
-/// Convert a callback function (that should call an external function) from one
-/// that can raise to one that will return a Result.
-@external(javascript, "../../ffi_exceptions.mjs", "resultify")
-pub fn resultify(callback callback: fn() -> CanRaise(a, b)) -> Result(a, b)
diff --git a/src/gloss/utils/fs.gleam b/src/gloss/utils/fs.gleam
deleted file mode 100644
index 730f653..0000000
--- a/src/gloss/utils/fs.gleam
+++ /dev/null
@@ -1,63 +0,0 @@
-import gleam/result
-import gleam/list
-import gleam/javascript/array.{type Array}
-import gloss/utils/buffer.{type Buffer}
-import gloss/utils/exceptions.{type CanRaise}
-
-pub type FSError
-
-pub fn read_file(path: String) -> Result(String, FSError) {
-  use contents <- result.try(exceptions.resultify(fn() { do_read_file(path) }))
-
-  Ok(buffer.to_string(contents))
-}
-
-pub fn readdir(path: String) -> Result(List(String), FSError) {
-  use files <- result.try(exceptions.resultify(fn() { do_readdir(path) }))
-
-  Ok(list.map(array.to_list(files), buffer.to_string))
-}
-
-pub fn mkdir(path: String) -> Result(Nil, FSError) {
-  use _undefined <- result.try(exceptions.resultify(fn() { do_mkdir(path) }))
-
-  Ok(Nil)
-}
-
-pub fn mkdir_p(path: String) -> Result(String, FSError) {
-  use created <- result.try(exceptions.resultify(fn() { do_mkdir_p(path) }))
-
-  Ok(created)
-}
-
-pub fn exists(path: String) -> Result(Bool, FSError) {
-  use created <- result.try(exceptions.resultify(fn() { do_exists(path) }))
-
-  Ok(created)
-}
-
-pub fn write_file(path: String, data: String) -> Result(Nil, FSError) {
-  use _undefined <- result.try(
-    exceptions.resultify(fn() { do_write_file(path, data) }),
-  )
-
-  Ok(Nil)
-}
-
-@external(javascript, "fs", "readFileSync")
-fn do_read_file(path: String) -> CanRaise(Buffer, FSError)
-
-@external(javascript, "fs", "readdirSync")
-fn do_readdir(path: String) -> CanRaise(Array(Buffer), FSError)
-
-@external(javascript, "fs", "mkdirSync")
-fn do_mkdir(path: String) -> CanRaise(Nil, FSError)
-
-@external(javascript, "../../ffi_fs.mjs", "mkdirP")
-fn do_mkdir_p(path: String) -> CanRaise(String, FSError)
-
-@external(javascript, "fs", "existsSync")
-fn do_exists(path: String) -> CanRaise(Bool, FSError)
-
-@external(javascript, "fs", "writeFileSync")
-fn do_write_file(path: String, data: String) -> CanRaise(Nil, FSError)
diff --git a/src/gloss/utils/ints/day.gleam b/src/gloss/utils/ints/day.gleam
index 88d3f34..a84e99e 100644
--- a/src/gloss/utils/ints/day.gleam
+++ b/src/gloss/utils/ints/day.gleam
@@ -1,3 +1,5 @@
+//// A day is a ranged integer from 1 to 31.
+
 import bigi.{type BigInt}
 import ranged_int/interface.{type Interface, Interface}
 
diff --git a/src/gloss/utils/ints/hour.gleam b/src/gloss/utils/ints/hour.gleam
index b807fcc..d173afb 100644
--- a/src/gloss/utils/ints/hour.gleam
+++ b/src/gloss/utils/ints/hour.gleam
@@ -1,3 +1,5 @@
+//// An hour is a ranged integer from 0 to 23.
+
 import bigi.{type BigInt}
 import ranged_int/interface.{type Interface, Interface}
 
diff --git a/src/gloss/utils/ints/minute.gleam b/src/gloss/utils/ints/minute.gleam
index 85d7c47..ee6ccf1 100644
--- a/src/gloss/utils/ints/minute.gleam
+++ b/src/gloss/utils/ints/minute.gleam
@@ -1,3 +1,5 @@
+//// A minute is a ranged integer from 0 to 59.
+
 import bigi.{type BigInt}
 import ranged_int/interface.{type Interface, Interface}
 
diff --git a/src/gloss/utils/luxon.gleam b/src/gloss/utils/luxon.gleam
index 290e84c..6082731 100644
--- a/src/gloss/utils/luxon.gleam
+++ b/src/gloss/utils/luxon.gleam
@@ -1,13 +1,18 @@
+//// Bindings to the Luxon library.
+
 import gloss/utils/date.{type Date}
 import gloss/utils/time.{type Time}
 
+/// Luxon DateTime.
 pub type DateTime
 
+/// Get a Luxon DateTime in the given timezone.
 pub fn date_time_in_zone(date: Date, time: Time, tz: String) {
   let datetime_str = date.format_iso(date) <> "T" <> time.format(time)
   do_date_time_in_zone(datetime_str, tz)
 }
 
+/// Get the current time as UTC.
 @external(javascript, "../../ffi_luxon.mjs", "utcNow")
 pub fn utc_now() -> DateTime
 
@@ -17,8 +22,6 @@ fn do_date_time_in_zone(
   tz: String,
 ) -> Result(DateTime, Nil)
 
-@external(javascript, "../../ffi_luxon.mjs", "toRFC2822")
-pub fn to_rfc_2822(dt: DateTime) -> String
-
+/// Format the DateTime as an ISO 8601 format string.
 @external(javascript, "../../ffi_luxon.mjs", "toISO")
 pub fn to_iso(dt: DateTime) -> String
diff --git a/src/gloss/utils/marked.gleam b/src/gloss/utils/marked.gleam
index a6d15c4..baf01ef 100644
--- a/src/gloss/utils/marked.gleam
+++ b/src/gloss/utils/marked.gleam
@@ -1,24 +1,32 @@
-import gloss/utils/object.{type Object}
+//// Bindings to the marked.js library.
 
+import gloss/internal/utils/object.{type Object}
+
+/// Marked.js options object.
 pub type Options =
   Object
 
+/// Create a new options object.
 pub fn new_options() -> Options {
   object.new()
 }
 
+/// Set the `mangle` option on or off.
 pub fn set_mangle(options: Options, do_mangle: Bool) -> Options {
   object.set(options, "mangle", do_mangle)
 }
 
+/// Set the `headerIds` option on or off.
 pub fn set_header_ids(options: Options, ids: Bool) -> Options {
   object.set(options, "headerIds", ids)
 }
 
+/// Set the `headerPrefix` option.
 pub fn set_header_prefix(options: Options, prefix: String) -> Options {
   object.set(options, "headerPrefix", prefix)
 }
 
+/// Parse a string containing Markdown using the default options.
 pub fn default_parse(content: String) -> String {
   let options =
     new_options()
@@ -29,5 +37,6 @@ pub fn default_parse(content: String) -> String {
   parse(content, options)
 }
 
+/// Parse a string containing Markdown using Marked.js.
 @external(javascript, "../../priv/vendor/marked.esm.mjs", "parse")
 pub fn parse(content content: String, options options: Options) -> String
diff --git a/src/gloss/utils/meta_url.gleam b/src/gloss/utils/meta_url.gleam
deleted file mode 100644
index fb8eec2..0000000
--- a/src/gloss/utils/meta_url.gleam
+++ /dev/null
@@ -1,2 +0,0 @@
-@external(javascript, "../../ffi_meta_url.mjs", "metaURL")
-pub fn get() -> String
diff --git a/src/gloss/utils/priv.gleam b/src/gloss/utils/priv.gleam
index 5ca2b54..fd2f897 100644
--- a/src/gloss/utils/priv.gleam
+++ b/src/gloss/utils/priv.gleam
@@ -1,7 +1,8 @@
 import gleam/uri
-import gloss/utils/meta_url
-import gloss/utils/path
+import gloss/internal/utils/meta_url
+import gloss/internal/utils/path
 
+/// Get the path to the `priv` directory of `gloss`.
 pub fn path() -> String {
   let assert Ok(meta_url) = uri.parse(meta_url.get())
 
diff --git a/src/gloss/utils/string.gleam b/src/gloss/utils/string.gleam
deleted file mode 100644
index 4df7b43..0000000
--- a/src/gloss/utils/string.gleam
+++ /dev/null
@@ -1,9 +0,0 @@
-import gleam/string
-
-/// Split the given string at the given index
-pub fn split_at(str: String, index: Int) -> #(String, String) {
-  let len = string.length(str)
-  let first = string.slice(str, 0, index)
-  let rest = string.slice(str, index, len - index)
-  #(first, rest)
-}
diff --git a/src/gloss/utils/time.gleam b/src/gloss/utils/time.gleam
index 6606afc..e1e72dd 100644
--- a/src/gloss/utils/time.gleam
+++ b/src/gloss/utils/time.gleam
@@ -16,6 +16,7 @@ pub fn compare(a: Time, b: Time) -> Order {
   }
 }
 
+/// Parse a time from an `hh:mm` format string.
 pub fn parse(str: String) {
   case string.split(str, ":") {
     [hours, minutes] ->
@@ -31,12 +32,14 @@ pub fn parse(str: String) {
   }
 }
 
+/// Format a time to an `hh:mm` format string.
 pub fn format(time: Time) -> String {
   pad(int.to_string(hour.to_int(time.hours)))
   <> ":"
   <> pad(int.to_string(minute.to_int(time.minutes)))
 }
 
+/// Get a time at hour 0 and minute 0.
 pub fn nil_time() {
   let assert Ok(h) = hour.from_int(0)
   let assert Ok(m) = minute.from_int(0)
diff --git a/src/gloss/utils/uniqid.gleam b/src/gloss/utils/uniqid.gleam
index 7f655b3..ef10d85 100644
--- a/src/gloss/utils/uniqid.gleam
+++ b/src/gloss/utils/uniqid.gleam
@@ -1,16 +1,20 @@
 import bigi.{type BigInt}
 
+/// A unique ID.
 pub type UniqID =
   BigInt
 
+/// Unique ID generator.
 pub opaque type Generator {
   Generator(id: BigInt)
 }
 
+/// Get a new generator.
 pub fn new() -> Generator {
   Generator(bigi.zero())
 }
 
+/// Get a unique ID and a new generator, that can be used to generate a new ID.
 pub fn get(gen: Generator) -> #(UniqID, Generator) {
   let new = bigi.add(gen.id, bigi.from_int(1))
   #(new, Generator(new))
diff --git a/src/gloss/writer.gleam b/src/gloss/writer.gleam
index bf9a775..72a7518 100644
--- a/src/gloss/writer.gleam
+++ b/src/gloss/writer.gleam
@@ -7,11 +7,12 @@ import lustre/ssg/xml
 import lustre/element
 import gloss/rendering/database.{type RenderDatabase} as _
 import gloss/config.{type Configuration, WriteError}
+import gloss/utils/priv
 
 pub fn write(db: RenderDatabase, config: Configuration) {
   let site =
     ssg.new(config.output_path)
-    |> ssg.add_static_dir("./build/dev/javascript/gloss/priv/assets")
+    |> ssg.add_static_dir(priv.path() <> "/assets")
 
   let single_posts =
     db.single_posts