diff --git a/rust/rox/Cargo.lock b/rust/rox/Cargo.lock
index 3103be5..169f10a 100644
--- a/rust/rox/Cargo.lock
+++ b/rust/rox/Cargo.lock
@@ -247,6 +247,8 @@ name = "rox"
 version = "0.1.0"
 dependencies = [
  "clap",
+ "lazy_static",
+ "thiserror",
  "tracing",
  "tracing-subscriber",
 ]
@@ -283,6 +285,26 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "thiserror"
+version = "2.0.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d452f284b73e6d76dd36758a0c8684b1d5be31f92b89d07fd5822175732206fc"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "2.0.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26afc1baea8a989337eeb52b6e72a039780ce45c3edfcc9c5b9d112feeb173c2"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "thread_local"
 version = "1.1.8"
diff --git a/rust/rox/Cargo.toml b/rust/rox/Cargo.toml
index 9c77e69..9b1332a 100644
--- a/rust/rox/Cargo.toml
+++ b/rust/rox/Cargo.toml
@@ -7,5 +7,7 @@ authors = ["Sebastian Hugentobler <shu@vanwa.ch>"]
 
 [dependencies]
 clap = { version = "4.5.28", features = ["derive"] }
+lazy_static = "1.5.0"
+thiserror = "2.0.11"
 tracing = "0.1.41"
 tracing-subscriber = { version = "0.3.19", features = ["env-filter"] }
diff --git a/rust/rox/src/keywords.rs b/rust/rox/src/keywords.rs
new file mode 100644
index 0000000..23743a5
--- /dev/null
+++ b/rust/rox/src/keywords.rs
@@ -0,0 +1,25 @@
+use crate::token::TokenType::{self, *};
+use lazy_static::lazy_static;
+use std::collections::HashMap;
+
+lazy_static! {
+    pub static ref KEYWORDS: HashMap<std::string::String, TokenType> = {
+        let mut m = HashMap::new();
+        m.insert("and".into(), And);
+        m.insert("class".into(), Class);
+        m.insert("else".into(), Else);
+        m.insert("false".into(), False);
+        m.insert("for".into(), For);
+        m.insert("fun".into(), Fun);
+        m.insert("if".into(), If);
+        m.insert("nil".into(), Nil);
+        m.insert("or".into(), Or);
+        m.insert("print".into(), Print);
+        m.insert("return".into(), Return);
+        m.insert("super".into(), Super);
+        m.insert("true".into(), True);
+        m.insert("var".into(), Var);
+        m.insert("while".into(), While);
+        m
+    };
+}
diff --git a/rust/rox/src/lib.rs b/rust/rox/src/lib.rs
index fe8e646..adf569e 100644
--- a/rust/rox/src/lib.rs
+++ b/rust/rox/src/lib.rs
@@ -1,6 +1,45 @@
-use std::path::Path;
+use std::{
+    fs::{self},
+    io::{self, Write},
+    path::Path,
+};
+
+use tracing::error;
 
 pub mod cli;
+pub mod keywords;
+pub mod scanner;
+pub mod token;
+pub mod tokenizer {
+    pub mod comment;
+    pub mod identifier;
+    pub mod interface;
+    pub mod lookahead;
+    pub mod newline;
+    pub mod number;
+    pub mod single_char;
+    pub mod string;
+    pub mod whitespace;
+}
 
-pub fn compile(source: &Path) {}
-pub fn repl() {}
+pub fn compile(source: &Path) -> Result<(), io::Error> {
+    let input = fs::read_to_string(source)?;
+    let _tokens = scanner::tokenize(&input);
+
+    Ok(())
+}
+
+pub fn repl() {
+    loop {
+        print!("> ");
+        let _ = io::stdout().flush();
+
+        let mut input = String::new();
+        match io::stdin().read_line(&mut input) {
+            Ok(_) => {}
+            Err(e) => error!("{}", e),
+        }
+        let input = input.trim().to_string();
+        let _tokens = scanner::tokenize(&input);
+    }
+}
diff --git a/rust/rox/src/main.rs b/rust/rox/src/main.rs
index 4686b71..4c38f72 100644
--- a/rust/rox/src/main.rs
+++ b/rust/rox/src/main.rs
@@ -1,5 +1,8 @@
+use std::process::exit;
+
 use clap::Parser;
 use rox::cli::{Cli, Commands};
+use tracing::error;
 
 fn main() {
     if std::env::var_os("RUST_LOG").is_none() {
@@ -11,7 +14,21 @@ fn main() {
 
     match &cli.command {
         Commands::Compile(compile_config) => {
-            rox::compile(&compile_config.source);
+            if !&compile_config.source.exists() {
+                error!(
+                    "{} does not exist",
+                    &compile_config.source.to_string_lossy()
+                );
+                exit(1);
+            }
+
+            if let Err(e) = rox::compile(&compile_config.source) {
+                error!(
+                    "failed to compile {}: {}",
+                    &compile_config.source.to_string_lossy(),
+                    e
+                );
+            }
         }
         Commands::Repl => {
             rox::repl();
diff --git a/rust/rox/src/scanner.rs b/rust/rox/src/scanner.rs
new file mode 100644
index 0000000..4a94dc8
--- /dev/null
+++ b/rust/rox/src/scanner.rs
@@ -0,0 +1,60 @@
+use crate::{
+    token::{Token, TokenType::Eof},
+    tokenizer::{
+        comment::Comment, identifier::Identifier, interface::Tokenizer, lookahead::Lookahead,
+        newline::Newline, number::Number, single_char::SingleChar, string::String,
+        whitespace::Whitespace,
+    },
+};
+use lazy_static::lazy_static;
+use tracing::{debug, error};
+
+lazy_static! {
+    static ref TOKENIZERS: Vec<Box<dyn Tokenizer>> = vec![
+        Box::new(SingleChar),
+        Box::new(Whitespace),
+        Box::new(Newline),
+        Box::new(Lookahead),
+        Box::new(Comment),
+        Box::new(String),
+        Box::new(Number),
+        Box::new(Identifier),
+    ];
+}
+
+pub fn tokenize(source: &str) -> Vec<Token> {
+    let mut tokens: Vec<Token> = Vec::new();
+    let mut source_chars = source.char_indices().peekable();
+
+    let mut line = 1;
+    while let Some(c) = source_chars.next() {
+        let mut tokenizer_idx = 0;
+        let mut tokenizer_result = None;
+        while tokenizer_idx < TOKENIZERS.len() && tokenizer_result.is_none() {
+            tokenizer_result = TOKENIZERS[tokenizer_idx].run(c, &mut source_chars, source, line);
+            tokenizer_idx += 1;
+        }
+
+        match tokenizer_result {
+            Some((line_advance, token)) => {
+                line += line_advance;
+
+                if let Some(token) = token {
+                    tokens.push(token);
+                }
+            }
+            None => {
+                error!("unexpected character: {}", c.1)
+            }
+        }
+    }
+    tokens.push(Token {
+        token_type: Eof,
+        lexeme: "".to_string(),
+        literal: None,
+        line,
+    });
+    debug!("{:?}", tokens);
+
+    tokens
+}
diff --git a/rust/rox/src/token.rs b/rust/rox/src/token.rs
new file mode 100644
index 0000000..192afa6
--- /dev/null
+++ b/rust/rox/src/token.rs
@@ -0,0 +1,76 @@
+use std::fmt::Display;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum TokenType {
+    // Single-character tokens.
+    LeftParen,
+    RightParen,
+    LeftBrace,
+    RightBrace,
+    Comma,
+    Dot,
+    Minus,
+    Plus,
+    Semicolon,
+    Slash,
+    Star,
+
+    // One or two character tokens.
+    Bang,
+    BangEqual,
+    Equal,
+    EqualEqual,
+    Greater,
+    GreaterEqual,
+    Less,
+    LessEqual,
+
+    // Literals.
+    Identifier,
+    String,
+    Number,
+
+    // Keywords.
+    And,
+    Class,
+    Else,
+    False,
+    Fun,
+    For,
+    If,
+    Nil,
+    Or,
+    Print,
+    Return,
+    Super,
+    This,
+    True,
+    Var,
+    While,
+
+    Eof,
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum Literal {
+    String(String),
+    Number(f64),
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct Token {
+    pub token_type: TokenType,
+    pub lexeme: String,
+    pub literal: Option<Literal>,
+    pub line: usize,
+}
+
+impl Display for Token {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "{}: {:?} {} {:?}",
+            self.line, self.token_type, self.lexeme, self.literal
+        )
+    }
+}
diff --git a/rust/rox/src/tokenizer/comment.rs b/rust/rox/src/tokenizer/comment.rs
new file mode 100644
index 0000000..0a1d4c2
--- /dev/null
+++ b/rust/rox/src/tokenizer/comment.rs
@@ -0,0 +1,39 @@
+use crate::token::TokenType::Slash;
+use std::{iter::Peekable, str::CharIndices};
+
+use crate::token::Token;
+
+use super::interface::Tokenizer;
+
+pub struct Comment;
+impl Tokenizer for Comment {
+    fn run(
+        &self,
+        c: (usize, char),
+        chars: &mut Peekable<CharIndices<'_>>,
+        source: &str,
+        line: usize,
+    ) -> Option<(usize, Option<Token>)> {
+        match c.1 {
+            '/' => {
+                let (line_advance, token) = if chars.next_if(|(_, peek)| *peek == '/').is_some() {
+                    while chars.next_if(|(_, peek)| *peek != '\n').is_some() {}
+                    chars.next();
+                    (1, None)
+                } else {
+                    (
+                        0,
+                        Some(Token {
+                            token_type: Slash,
+                            lexeme: source[c.0..=c.0].to_string(),
+                            literal: None,
+                            line,
+                        }),
+                    )
+                };
+                Some((line_advance, token))
+            }
+            _ => None,
+        }
+    }
+}
diff --git a/rust/rox/src/tokenizer/identifier.rs b/rust/rox/src/tokenizer/identifier.rs
new file mode 100644
index 0000000..31952bf
--- /dev/null
+++ b/rust/rox/src/tokenizer/identifier.rs
@@ -0,0 +1,42 @@
+use crate::{
+    keywords::KEYWORDS,
+    token::{Token, TokenType},
+};
+use std::{iter::Peekable, str::CharIndices};
+
+use super::interface::Tokenizer;
+
+pub struct Identifier;
+impl Tokenizer for Identifier {
+    fn run(
+        &self,
+        c: (usize, char),
+        chars: &mut Peekable<CharIndices<'_>>,
+        source: &str,
+        line: usize,
+    ) -> Option<(usize, Option<Token>)> {
+        if c.1.is_alphabetic() || c.1 == '_' {
+            let mut end_idx = c.0;
+            while let Some((idx, _)) = chars.next_if(|(_, x)| x.is_alphanumeric() || c.1 == '_') {
+                end_idx = idx;
+            }
+
+            let lexeme = source[c.0..=end_idx].to_string();
+            let token_type = match KEYWORDS.get(&lexeme) {
+                Some(token_type) => *token_type,
+                None => TokenType::Identifier,
+            };
+            Some((
+                0,
+                Some(Token {
+                    token_type,
+                    lexeme,
+                    literal: None,
+                    line,
+                }),
+            ))
+        } else {
+            None
+        }
+    }
+}
diff --git a/rust/rox/src/tokenizer/interface.rs b/rust/rox/src/tokenizer/interface.rs
new file mode 100644
index 0000000..7b1e63b
--- /dev/null
+++ b/rust/rox/src/tokenizer/interface.rs
@@ -0,0 +1,13 @@
+use std::{iter::Peekable, str::CharIndices};
+
+use crate::token::Token;
+
+pub trait Tokenizer: Send + Sync {
+    fn run(
+        &self,
+        c: (usize, char),
+        chars: &mut Peekable<CharIndices<'_>>,
+        source: &str,
+        line: usize,
+    ) -> Option<(usize, Option<Token>)>;
+}
diff --git a/rust/rox/src/tokenizer/lookahead.rs b/rust/rox/src/tokenizer/lookahead.rs
new file mode 100644
index 0000000..6e0294e
--- /dev/null
+++ b/rust/rox/src/tokenizer/lookahead.rs
@@ -0,0 +1,91 @@
+use super::interface::Tokenizer;
+use crate::token::TokenType::*;
+use crate::token::{Token, TokenType};
+use lazy_static::lazy_static;
+use std::{collections::HashMap, iter::Peekable, str::CharIndices};
+
+struct LookaheadEntry {
+    default_token: TokenType,
+    lookahead_map: HashMap<char, TokenType>,
+}
+
+lazy_static! {
+    static ref LOOKAHEAD_TOKENS: HashMap<char, LookaheadEntry> = {
+        let mut m = HashMap::new();
+
+        let mut bang_map = HashMap::new();
+        bang_map.insert('=', BangEqual);
+        m.insert(
+            '!',
+            LookaheadEntry {
+                default_token: Bang,
+                lookahead_map: bang_map,
+            },
+        );
+
+        let mut equal_map = HashMap::new();
+        equal_map.insert('=', EqualEqual);
+        m.insert(
+            '=',
+            LookaheadEntry {
+                default_token: Equal,
+                lookahead_map: equal_map,
+            },
+        );
+
+        let mut less_map = HashMap::new();
+        less_map.insert('=', LessEqual);
+        m.insert(
+            '<',
+            LookaheadEntry {
+                default_token: Less,
+                lookahead_map: less_map,
+            },
+        );
+
+        let mut greater_map = HashMap::new();
+        greater_map.insert('=', GreaterEqual);
+        m.insert(
+            '>',
+            LookaheadEntry {
+                default_token: Greater,
+                lookahead_map: greater_map,
+            },
+        );
+
+        m
+    };
+}
+
+pub struct Lookahead;
+impl Tokenizer for Lookahead {
+    fn run(
+        &self,
+        c: (usize, char),
+        chars: &mut Peekable<CharIndices<'_>>,
+        source: &str,
+        line: usize,
+    ) -> Option<(usize, Option<Token>)> {
+        LOOKAHEAD_TOKENS.get(&c.1).map(|entry| {
+            let (lexeme, token_type) = if let Some(&(_, peeked)) = chars.peek() {
+                if let Some(&token_type) = entry.lookahead_map.get(&peeked) {
+                    chars.next();
+                    (source[c.0..=c.0 + 1].to_string(), token_type)
+                } else {
+                    (source[c.0..=c.0].to_string(), entry.default_token)
+                }
+            } else {
+                (source[c.0..=c.0].to_string(), entry.default_token)
+            };
+            (
+                0,
+                Some(Token {
+                    token_type,
+                    lexeme,
+                    literal: None,
+                    line,
+                }),
+            )
+        })
+    }
+}
diff --git a/rust/rox/src/tokenizer/newline.rs b/rust/rox/src/tokenizer/newline.rs
new file mode 100644
index 0000000..74827d3
--- /dev/null
+++ b/rust/rox/src/tokenizer/newline.rs
@@ -0,0 +1,19 @@
+use super::interface::Tokenizer;
+use crate::token::Token;
+use std::{iter::Peekable, str::CharIndices};
+
+pub struct Newline;
+impl Tokenizer for Newline {
+    fn run(
+        &self,
+        c: (usize, char),
+        _chars: &mut Peekable<CharIndices<'_>>,
+        _source: &str,
+        _line: usize,
+    ) -> Option<(usize, Option<Token>)> {
+        match c.1 {
+            '\n' => Some((1, None)),
+            _ => None,
+        }
+    }
+}
diff --git a/rust/rox/src/tokenizer/number.rs b/rust/rox/src/tokenizer/number.rs
new file mode 100644
index 0000000..b6766cd
--- /dev/null
+++ b/rust/rox/src/tokenizer/number.rs
@@ -0,0 +1,45 @@
+use crate::token::{Literal, Token, TokenType};
+use std::{iter::Peekable, str::CharIndices};
+use tracing::error;
+
+use super::interface::Tokenizer;
+
+pub struct Number;
+impl Tokenizer for Number {
+    fn run(
+        &self,
+        c: (usize, char),
+        chars: &mut Peekable<CharIndices<'_>>,
+        source: &str,
+        line: usize,
+    ) -> Option<(usize, Option<Token>)> {
+        if c.1.is_ascii_digit() {
+            let mut end_idx = c.0;
+            while let Some((idx, _)) = chars.next_if(|(_, x)| x.is_ascii_digit()) {
+                end_idx = idx;
+            }
+            chars.next_if(|(_, x)| *x == '.');
+            while let Some((idx, _)) = chars.next_if(|(_, x)| x.is_ascii_digit()) {
+                end_idx = idx;
+            }
+
+            let lexeme = source[c.0..=end_idx].to_string();
+            let token = match lexeme.parse::<f64>() {
+                Ok(literal) => Some(Token {
+                    token_type: TokenType::Number,
+                    lexeme,
+                    literal: Some(Literal::Number(literal)),
+                    line,
+                }),
+                Err(e) => {
+                    error!("failed to parse number: {e}");
+                    None
+                }
+            };
+
+            Some((0, token))
+        } else {
+            None
+        }
+    }
+}
diff --git a/rust/rox/src/tokenizer/single_char.rs b/rust/rox/src/tokenizer/single_char.rs
new file mode 100644
index 0000000..18e04b3
--- /dev/null
+++ b/rust/rox/src/tokenizer/single_char.rs
@@ -0,0 +1,49 @@
+use super::interface::Tokenizer;
+use crate::token::{
+    Token,
+    TokenType::{self, *},
+};
+use lazy_static::lazy_static;
+use std::{collections::HashMap, iter::Peekable, str::CharIndices};
+
+lazy_static! {
+    static ref SINGLE_CHAR_TOKENS: HashMap<char, TokenType> = {
+        let mut m = HashMap::new();
+        m.insert('(', LeftParen);
+        m.insert(')', RightParen);
+        m.insert('{', LeftBrace);
+        m.insert('}', RightBrace);
+        m.insert(',', Comma);
+        m.insert('.', Dot);
+        m.insert('-', Minus);
+        m.insert('+', Plus);
+        m.insert(';', Semicolon);
+        m.insert('*', Star);
+        m
+    };
+}
+
+pub struct SingleChar;
+impl Tokenizer for SingleChar {
+    fn run(
+        &self,
+        c: (usize, char),
+        _chars: &mut Peekable<CharIndices<'_>>,
+        source: &str,
+        line: usize,
+    ) -> Option<(usize, Option<Token>)> {
+        let lexeme = source[c.0..=c.0].to_string();
+
+        SINGLE_CHAR_TOKENS.get(&c.1).map(|token_type| {
+            (
+                0,
+                Some(Token {
+                    token_type: *token_type,
+                    lexeme,
+                    literal: None,
+                    line,
+                }),
+            )
+        })
+    }
+}
diff --git a/rust/rox/src/tokenizer/string.rs b/rust/rox/src/tokenizer/string.rs
new file mode 100644
index 0000000..07d6309
--- /dev/null
+++ b/rust/rox/src/tokenizer/string.rs
@@ -0,0 +1,48 @@
+use super::interface::Tokenizer;
+use crate::token::{Literal, Token, TokenType};
+use std::{iter::Peekable, str::CharIndices};
+use tracing::error;
+
+pub struct String;
+impl Tokenizer for String {
+    fn run(
+        &self,
+        c: (usize, char),
+        chars: &mut Peekable<CharIndices<'_>>,
+        source: &str,
+        line: usize,
+    ) -> Option<(usize, Option<Token>)> {
+        match c.1 {
+            '"' => {
+                let mut lines = 0;
+                while let Some((_, c)) = chars.next_if(|(_, peek)| *peek != '"') {
+                    if c == '\n' {
+                        lines += 1;
+                    }
+                }
+
+                match chars.next_if(|(_, x)| *x == '"') {
+                    Some((end_idx, _)) => {
+                        let lexeme = source[c.0..=end_idx].to_string();
+                        let literal = source[c.0 + 1..end_idx].to_string();
+
+                        Some((
+                            lines,
+                            Some(Token {
+                                token_type: TokenType::String,
+                                lexeme,
+                                literal: Some(Literal::String(literal)),
+                                line,
+                            }),
+                        ))
+                    }
+                    None => {
+                        error!("unterminated string");
+                        None
+                    }
+                }
+            }
+            _ => None,
+        }
+    }
+}
diff --git a/rust/rox/src/tokenizer/whitespace.rs b/rust/rox/src/tokenizer/whitespace.rs
new file mode 100644
index 0000000..a47f5c2
--- /dev/null
+++ b/rust/rox/src/tokenizer/whitespace.rs
@@ -0,0 +1,19 @@
+use super::interface::Tokenizer;
+use crate::token::Token;
+use std::{iter::Peekable, str::CharIndices};
+
+pub struct Whitespace;
+impl Tokenizer for Whitespace {
+    fn run(
+        &self,
+        c: (usize, char),
+        _chars: &mut Peekable<CharIndices<'_>>,
+        _source: &str,
+        _line: usize,
+    ) -> Option<(usize, Option<Token>)> {
+        match c.1 {
+            ' ' | '\r' | '\t' => Some((0, None)),
+            _ => None,
+        }
+    }
+}