diff --git a/guess-mime-type/Makefile b/guess-mime-type/Makefile
new file mode 100644
index 0000000..5f05db0
--- /dev/null
+++ b/guess-mime-type/Makefile
@@ -0,0 +1,24 @@
+CC = gcc
+CFLAGS = -Wall -Wextra
+
+all: test
+
+test: testGuess
+	./testGuess
+
+testGuess: build/mimetype.o build/testGuess.o
+	$(CC) -o $@ $^
+
+build/mimetype.o: src/mimetype.c src/mimetype.h | build
+	$(CC) $(CFLAGS) -c $< -o $@
+
+build/testGuess.o: test/testGuess.c src/mimetype.h | build
+	$(CC) $(CFLAGS) -Isrc/ -c $< -o $@
+
+build:
+	mkdir build
+
+clean:
+	rm -rf testGuess build
+
+.PHONY: all test clean
diff --git a/guess-mime-type/oki.toml b/guess-mime-type/oki.toml
new file mode 100644
index 0000000..5b7081d
--- /dev/null
+++ b/guess-mime-type/oki.toml
@@ -0,0 +1,5 @@
+[package]
+name = "guess-mime-type"
+version = "0.1.0"
+description = "Guess mime type from a filename"
+license = "MIT"
diff --git a/guess-mime-type/src/mimetype.c b/guess-mime-type/src/mimetype.c
new file mode 100644
index 0000000..c3a3b26
--- /dev/null
+++ b/guess-mime-type/src/mimetype.c
@@ -0,0 +1,41 @@
+#include "mimetype.h"
+
+#include <string.h>
+
+const char *guessMimeType(const char *filename) {
+	const char *dot = strrchr(filename, '.');
+	if (!dot || dot == filename) {
+		return "application/octet-stream";
+	}
+	const char *extension = dot + 1;
+	if (!extension) {
+		return "text/plain";
+	}
+
+	if (strcmp("avif", extension) == 0) {
+		return "image/avif";
+	} else if (strcmp("css", extension) == 0) {
+		return "text/css";
+	} else if (strcmp("csv", extension) == 0) {
+		return "text/csv";
+	} else if (strcmp("gif", extension) == 0) {
+		return "image/gif";
+	} else if (strcmp("html", extension) == 0) {
+		return "text/html";
+	} else if (strcmp("jpg", extension) == 0 || strcmp("jpeg", extension) == 0) {
+		return "image/jpeg";
+	} else if (strcmp("js", extension) == 0) {
+		return "application/javascript";
+	} else if (strcmp("json", extension) == 0) {
+		return "application/json";
+	} else if (strcmp("pdf", extension) == 0) {
+		return "application/pdf";
+	} else if (strcmp("png", extension) == 0) {
+		return "image/png";
+	} else if (strcmp("svg", extension) == 0) {
+		return "image/svg+xml";
+	} else if (strcmp("webp", extension) == 0) {
+		return "image/webp";
+	}
+	return "text/plain";
+}
diff --git a/guess-mime-type/src/mimetype.h b/guess-mime-type/src/mimetype.h
new file mode 100644
index 0000000..bf877e5
--- /dev/null
+++ b/guess-mime-type/src/mimetype.h
@@ -0,0 +1,12 @@
+#ifndef GUESS_MIME_TYPE_H
+#define GUESS_MIME_TYPE_H
+
+/**
+ * Guess the mime type of a file from its extension.
+ *
+ * @param filename The file name
+ * @return The mime type deduced from common web extensions
+ */
+const char *guessMimeType(const char *filename);
+
+#endif // GUESS_MIME_TYPE_H
diff --git a/guess-mime-type/test/testGuess.c b/guess-mime-type/test/testGuess.c
new file mode 100644
index 0000000..01a9b74
--- /dev/null
+++ b/guess-mime-type/test/testGuess.c
@@ -0,0 +1,14 @@
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "mimetype.h"
+
+int main(void) {
+	assert(strcmp(guessMimeType("/tmp/file"), "application/octet-stream") == 0);
+	assert(strcmp(guessMimeType("www/car.avif"), "image/avif") == 0);
+	assert(strcmp(guessMimeType("css.html"), "text/html") == 0);
+	assert(strcmp(guessMimeType("html.css.js"), "application/javascript") == 0);
+	printf("Success!\n");
+	return 0;
+}