diff --git a/README.md b/README.md
index 7db0c24..17f6cd0 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,14 @@ Cisastor is a collection of C libraries and utilities.
 
 - [Testing Guide](docs/testing/how-to.md) - Learn how to write and run tests using the built-in testing framework.
 
+### Libraries
+
+- [Arena Allocator](docs/libs/arena_allocator.md)
+- [Data Containers](docs/libs/data_containers.md) (ArrayList, Iterator, StringView)
+- [Progress Bar](docs/libs/progressbar.md)
+- [Testing Framework](docs/libs/testing.md)
+- [Utils](docs/libs/utils.md)
+
 ## Project Structure
 
 - `libs/`: Core libraries.
diff --git a/docs/libs/arena_allocator.md b/docs/libs/arena_allocator.md
new file mode 100644
index 0000000..6460ebd
--- /dev/null
+++ b/docs/libs/arena_allocator.md
@@ -0,0 +1,21 @@
+# Arena Allocator
+
+A simple region-based memory allocator that manages memory in chunks.
+
+## API
+
+### Functions
+
+#### `void *arena_alloc(size_t size)`
+Allocates `size` bytes from the current arena chunk. If the current chunk is full or uninitialized, a new chunk is allocated. Memory is automatically freed when the program exits via `atexit`.
+
+#### `char *string_create_empty(size_t characters)`
+Allocates a null-terminated string of the given character length in the arena.
+
+### Macros
+
+#### `aalloc(size)`
+Alias for `arena_alloc(size)`.
+
+#### `reaalloc(a, b)`
+Alias for `aalloc(b)`. Note: Currently does not reallocate existing memory, just allocates a new block.
diff --git a/docs/libs/data_containers.md b/docs/libs/data_containers.md
new file mode 100644
index 0000000..0ddac66
--- /dev/null
+++ b/docs/libs/data_containers.md
@@ -0,0 +1,100 @@
+# Data Containers
+
+Collection of generic data structures and utilities.
+
+## Array List
+
+A dynamic array implementation similar to Go slices or C++ `std::vector`.
+
+### Type Safe API Generation
+Use the `array_list_init(type)` macro to generate type-safe wrapper functions.
+
+```c
+typedef struct foo { int id; } foo;
+array_list_init(foo);
+
+// Generated functions:
+struct array_list_foo *al = array_list_create_foo();
+foo f = {1};
+array_list_append_foo(al, f);
+foo *ptr = array_list_get_foo_at(al, 0);
+```
+
+### Core API
+
+#### `size_t array_list_get_length(struct array_list *al)`
+Returns the current number of elements.
+
+#### `size_t array_list_get_capacity(struct array_list *al)`
+Returns the current allocated capacity.
+
+#### `byte *array_list_get_element_at(struct array_list *al, int index)`
+Returns a pointer to the element at the given index, or `NULL` if out of bounds.
+
+#### `byte *array_list_append(struct array_list *al, const void *data)`
+Appends data to the list, reallocating if necessary. Returns a pointer to the newly added element.
+
+---
+
+## Iterator
+
+A generic iterator pattern for traversing containers.
+
+### Core API
+
+#### `struct iterator *iterator_begin(struct array_list *list)`
+Creates an iterator for an `array_list`.
+
+#### `void *iterator_end(struct iterator *it)`
+Returns a sentinel pointer representing the end of the container.
+
+#### `byte *iterator_element(struct iterator *it)`
+Returns the current element.
+
+#### `void iterator_increment(struct iterator *it)`
+Advances the iterator.
+
+### Mutating Iterators
+
+#### `struct iterator_mutating *iterator_map(struct iterator *it, iterator_map_predicate predicate, void *result_buffer)`
+Creates a mapping iterator.
+
+#### `struct iterator_mutating *iterator_filter(struct iterator *it, iterator_filter_predicate predicate)`
+Creates a filtering iterator.
+
+---
+
+## String View
+
+A non-owning view into a string, useful for parsing.
+
+### Core API
+
+#### `struct string_view *string_view_create(char *stream)`
+Creates a view for the given string.
+
+#### `char string_view_peek_char(struct string_view *sv)`
+Returns the current character without advancing the pointer.
+
+#### `char string_view_next_char(struct string_view *sv)`
+Returns the current character and advances the pointer.
+
+#### `int string_view_current_pos(struct string_view *sv)`
+Returns the index of the last character read (-1 initially).
+
+#### `char string_view_char_at(struct string_view *sv, int pos)`
+Returns the character at the absolute position in the original stream.
+
+#### `int string_view_compare_word(struct string_view *sv, const char *const word)`
+Checks if the next characters match `word`. Advances pointer on match. Returns 0 on success.
+
+### Consumption API
+
+#### `void string_view_consume_whitespace(struct string_view *sv)`
+Skips spaces and tabs.
+
+#### `const char *const string_view_consume_word(struct string_view *sv)`
+Consumes and returns an alphanumeric (plus underscore) word.
+
+#### `void string_consume_till_end_of_line(struct string_view *sv)`
+Advances the pointer to the next newline or end of string.
diff --git a/docs/libs/progressbar.md b/docs/libs/progressbar.md
new file mode 100644
index 0000000..d0e4fc5
--- /dev/null
+++ b/docs/libs/progressbar.md
@@ -0,0 +1,16 @@
+# Progress Bar
+
+A drop-in replacement for `std::ostream` like functionality to display progress in the terminal.
+
+## API
+
+### Types
+
+#### `ProgressBarOptions`
+- `int bytes_length`: Total size to reach 100%.
+- `char *label`: Label displayed next to the bar.
+
+### Functions
+
+#### `FILE *progressbar_open(FILE *fp, ProgressBarOptions *options)`
+Returns a `FILE` pointer that, when written to, updates the progress bar on `stderr` while passing data through to the original `fp`.
diff --git a/docs/libs/testing.md b/docs/libs/testing.md
new file mode 100644
index 0000000..e97c58d
--- /dev/null
+++ b/docs/libs/testing.md
@@ -0,0 +1,29 @@
+# Testing Framework
+
+A simple unit testing framework for Cisastor.
+
+## API
+
+### Defining Tests
+
+#### `TEST(name)` / `IT(name)`
+Defines a test function. Tests are automatically registered.
+
+### Assertions
+
+#### `cassert(cond, message)`
+Asserts that `cond` is true, otherwise fails the test with `message`.
+
+#### `cassertf(cond, fmt, ...)`
+Formatted version of `cassert`.
+
+#### `fail(message)` / `failf(fmt, ...)`
+Manually fails a test.
+
+### Utilities
+
+#### `uint8_t strcmp_at_any(const char *const src, const char *const match)`
+Checks if `match` is a substring of `src`.
+
+#### `uint8_t run_command(const char *const args)`
+Executes a shell command and prints output. Returns 0 on success.
diff --git a/docs/libs/utils.md b/docs/libs/utils.md
new file mode 100644
index 0000000..32c3eee
--- /dev/null
+++ b/docs/libs/utils.md
@@ -0,0 +1,16 @@
+# Utils
+
+Generic helper macros and types.
+
+## API
+
+### Macros
+
+#### `cast(type, value)`
+A macro for explicit casting: `((type)value)`.
+
+#### `null`
+Alias for `NULL`.
+
+#### `byte`
+Alias for `char`.