diff --git a/include/swaybar/tray/icon.h b/include/swaybar/tray/icon.h
new file mode 100644
index 00000000..7a6c400c
--- /dev/null
+++ b/include/swaybar/tray/icon.h
@@ -0,0 +1,44 @@
+#ifndef _SWAYBAR_TRAY_ICON_H
+#define _SWAYBAR_TRAY_ICON_H
+
+#include "list.h"
+
+enum subdir_type {
+	THRESHOLD,
+	SCALABLE,
+	FIXED
+};
+
+struct icon_theme_subdir {
+	char *name;
+	int size;
+	enum subdir_type type;
+	int max_size;
+	int min_size;
+	int threshold;
+};
+
+struct icon_theme {
+	char *name;
+	char *comment;
+	char *inherits;
+	list_t *directories; // char *
+
+	char *dir;
+	list_t *subdirs; // struct icon_theme_subdir *
+};
+
+void init_themes(list_t **themes, list_t **basedirs);
+void finish_themes(list_t *themes, list_t *basedirs);
+
+/*
+ * Finds an icon of a specified size given a list of themes and base directories.
+ * If the icon is found, the pointers min_size & max_size are set to minimum &
+ * maximum size that the icon can be scaled to, respectively.
+ * Returns: path of icon (which should be freed), or NULL if the icon is not found.
+ */
+char *find_icon(list_t *themes, list_t *basedirs, char *name, int size,
+		char *theme, int *min_size, int *max_size);
+char *find_icon_in_dir(char *name, char *dir, int *min_size, int *max_size);
+
+#endif
diff --git a/include/swaybar/tray/tray.h b/include/swaybar/tray/tray.h
index cc3e8133..8e15fb86 100644
--- a/include/swaybar/tray/tray.h
+++ b/include/swaybar/tray/tray.h
@@ -9,6 +9,7 @@
 #endif
 #include <cairo.h>
 #include <stdint.h>
+#include "list.h"
 
 struct swaybar;
 struct swaybar_output;
@@ -22,6 +23,9 @@ struct swaybar_tray {
 
 	struct swaybar_watcher *watcher_xdg;
 	struct swaybar_watcher *watcher_kde;
+
+	list_t *basedirs; // char *
+	list_t *themes; // struct swaybar_theme *
 };
 
 struct swaybar_tray *create_tray(struct swaybar *bar);
diff --git a/swaybar/meson.build b/swaybar/meson.build
index ef64f33a..b8ed2c23 100644
--- a/swaybar/meson.build
+++ b/swaybar/meson.build
@@ -1,4 +1,5 @@
 tray_files = get_option('enable-tray') ? [
+	'tray/icon.c',
 	'tray/tray.c',
 	'tray/watcher.c'
 ] : []
diff --git a/swaybar/tray/icon.c b/swaybar/tray/icon.c
new file mode 100644
index 00000000..67805858
--- /dev/null
+++ b/swaybar/tray/icon.c
@@ -0,0 +1,462 @@
+#define _POSIX_C_SOURCE 200809L
+#include <ctype.h>
+#include <dirent.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <wordexp.h>
+#include "swaybar/tray/icon.h"
+#include "config.h"
+#include "list.h"
+#include "log.h"
+#include "stringop.h"
+
+static bool dir_exists(char *path) {
+	struct stat sb;
+	return stat(path, &sb) == 0 && S_ISDIR(sb.st_mode);
+}
+
+static list_t *get_basedirs(void) {
+	list_t *basedirs = create_list();
+	list_add(basedirs, strdup("$HOME/.icons")); // deprecated
+
+	char *data_home = getenv("XDG_DATA_HOME");
+	list_add(basedirs, strdup(data_home && *data_home ?
+			"$XDG_DATA_HOME/icons" : "$HOME/.local/share/icons"));
+
+	list_add(basedirs, strdup("/usr/share/pixmaps"));
+
+	char *data_dirs = getenv("XDG_DATA_DIRS");
+	if (!(data_dirs && *data_dirs)) {
+		data_dirs = "/usr/local/share:/usr/share";
+	}
+	data_dirs = strdup(data_dirs);
+	char *dir = strtok(data_dirs, ":");
+	do {
+		size_t path_len = snprintf(NULL, 0, "%s/icons", dir) + 1;
+		char *path = malloc(path_len);
+		snprintf(path, path_len, "%s/icons", dir);
+		list_add(basedirs, path);
+	} while ((dir = strtok(NULL, ":")));
+	free(data_dirs);
+
+	list_t *basedirs_expanded = create_list();
+	for (int i = 0; i < basedirs->length; ++i) {
+		wordexp_t p;
+		if (wordexp(basedirs->items[i], &p, WRDE_UNDEF) == 0) {
+			if (dir_exists(p.we_wordv[0])) {
+				list_add(basedirs_expanded, strdup(p.we_wordv[0]));
+			}
+			wordfree(&p);
+		}
+	}
+
+	list_free_items_and_destroy(basedirs);
+
+	return basedirs_expanded;
+}
+
+static void destroy_theme(struct icon_theme *theme) {
+	if (!theme) {
+		return;
+	}
+	free(theme->name);
+	free(theme->comment);
+	free(theme->inherits);
+	list_free_items_and_destroy(theme->directories);
+	free(theme->dir);
+
+	for (int i = 0; i < theme->subdirs->length; ++i) {
+		struct icon_theme_subdir *subdir = theme->subdirs->items[i];
+		free(subdir->name);
+		free(subdir);
+	}
+	list_free(theme->subdirs);
+	free(theme);
+}
+
+static int cmp_group(const void *item, const void *cmp_to) {
+	return strcmp(item, cmp_to);
+}
+
+static bool group_handler(char *old_group, char *new_group,
+		struct icon_theme *theme) {
+	if (!old_group) { // first group must be "Icon Theme"
+		return strcmp(new_group, "Icon Theme");
+	}
+
+	if (strcmp(old_group, "Icon Theme") == 0) {
+		if (!(theme->name && theme->comment && theme->directories)) {
+			return true;
+		}
+	} else {
+		if (theme->subdirs->length == 0) { // skip
+			return false;
+		}
+
+		struct icon_theme_subdir *subdir =
+			theme->subdirs->items[theme->subdirs->length - 1];
+		if (!subdir->size) return true;
+
+		switch (subdir->type) {
+		case FIXED: subdir->max_size = subdir->min_size = subdir->size;
+			break;
+		case SCALABLE: {
+			if (!subdir->max_size) subdir->max_size = subdir->size;
+			if (!subdir->min_size) subdir->min_size = subdir->size;
+			break;
+		}
+		case THRESHOLD:
+			subdir->max_size = subdir->size + subdir->threshold;
+			subdir->min_size = subdir->size - subdir->threshold;
+		}
+	}
+
+	if (new_group && list_seq_find(theme->directories, cmp_group, new_group) != -1) {
+		struct icon_theme_subdir *subdir = calloc(1, sizeof(struct icon_theme_subdir));
+		if (!subdir) {
+			return true;
+		}
+		subdir->name = strdup(new_group);
+		subdir->threshold = 2;
+		list_add(theme->subdirs, subdir);
+	}
+
+	return false;
+}
+
+static int entry_handler(char *group, char *key, char *value,
+		struct icon_theme *theme) {
+	if (strcmp(group, "Icon Theme") == 0) {
+		if (strcmp(key, "Name") == 0) {
+			theme->name = strdup(value);
+		} else if (strcmp(key, "Comment") == 0) {
+			theme->comment = strdup(value);
+		} else if (strcmp(key, "Inherists") == 0) {
+			theme->inherits = strdup(value);
+		} else if (strcmp(key, "Directories") == 0) {
+			theme->directories = split_string(value, ",");
+		} // Ignored: ScaledDirectories, Hidden, Example
+	} else {
+		if (theme->subdirs->length == 0) { // skip
+			return false;
+		}
+
+		struct icon_theme_subdir *subdir =
+			theme->subdirs->items[theme->subdirs->length - 1];
+		if (strcmp(subdir->name, group) != 0) { // skip
+			return false;
+		}
+
+		char *end;
+		int n = strtol(value, &end, 10);
+		if (strcmp(key, "Size") == 0) {
+			subdir->size = n;
+			return *end != '\0';
+		} else if (strcmp(key, "Type") == 0) {
+			if (strcmp(value, "Fixed") == 0) {
+				subdir->type = FIXED;
+			} else if (strcmp(value, "Scalable") == 0) {
+				subdir->type = SCALABLE;
+			} else if (strcmp(value, "Threshold") == 0) {
+				subdir->type = THRESHOLD;
+			} else {
+				return true;
+			}
+		} else if (strcmp(key, "MaxSize") == 0) {
+			subdir->max_size = n;
+			return *end != '\0';
+		} else if (strcmp(key, "MinSize") == 0) {
+			subdir->min_size = n;
+			return *end != '\0';
+		} else if (strcmp(key, "Threshold") == 0) {
+			subdir->threshold = n;
+			return *end != '\0';
+		} // Ignored: Scale, Applications
+	}
+	return false;
+}
+
+/*
+ * This is a Freedesktop Desktop Entry parser (essentially INI)
+ * It calls entry_handler for every entry
+ * and group_handler between every group (as well as at both ends)
+ * Handlers return whether an error occured, which stops parsing
+ */
+static struct icon_theme *read_theme_file(char *basedir, char *theme_name) {
+	// look for index.theme file
+	size_t path_len = snprintf(NULL, 0, "%s/%s/index.theme", basedir,
+			theme_name) + 1;
+	char *path = malloc(path_len);
+	snprintf(path, path_len, "%s/%s/index.theme", basedir, theme_name);
+	FILE *theme_file = fopen(path, "r");
+	if (!theme_file) {
+		return NULL;
+	}
+
+	struct icon_theme *theme = calloc(1, sizeof(struct icon_theme));
+	if (!theme) {
+		return NULL;
+	}
+	theme->subdirs = create_list();
+
+	bool error = false;
+	char *group = NULL;
+	char *full_line = NULL;
+	size_t full_len = 0;
+	ssize_t nread;
+	while ((nread = getline(&full_line, &full_len, theme_file)) != -1) {
+		char *line = full_line - 1;
+		while (isspace(*++line)) {} // remove leading whitespace
+		if (!*line || line[0] == '#') continue; // ignore blank lines & comments
+
+		int len = nread - (line - full_line);
+		while (isspace(line[--len])) {}
+		line[++len] = '\0'; // remove trailing whitespace
+
+		if (line[0] == '[') { // group header
+			// check well-formed
+			if (line[--len] != ']') {
+				error = true;
+				break;
+			}
+			int i = 1;
+			for (; !iscntrl(line[i]) && line[i] != '[' && line[i] != ']'; ++i) {}
+			if (i < len) {
+				error = true;
+				break;
+			}
+
+			// call handler
+			line[len] = '\0';
+			error = group_handler(group, &line[1], theme);
+			if (error) {
+				break;
+			}
+			free(group);
+			group = strdup(&line[1]);
+		} else { // key-value pair
+			// check well-formed
+			int eok = 0;
+			for (; isalnum(line[eok]) || line[eok] == '-'; ++eok) {} // TODO locale?
+			int i = eok - 1;
+			while (isspace(line[++i])) {}
+			if (line[i] != '=') {
+				error = true;
+				break;
+			}
+
+			line[eok] = '\0'; // split into key-value pair
+			char *value = &line[i];
+			while (isspace(*++value)) {}
+			// TODO unescape value
+			error = entry_handler(group, line, value, theme);
+			if (error) {
+				break;
+			}
+		}
+	}
+
+	if (!error && group) {
+		error = group_handler(group, NULL, theme);
+	}
+
+	free(group);
+	free(full_line);
+	fclose(theme_file);
+
+	if (!error) {
+		theme->dir = strdup(theme_name);
+		return theme;
+	} else {
+		destroy_theme(theme);
+		return NULL;
+	}
+}
+
+static list_t *load_themes_in_dir(char *basedir) {
+	DIR *dir;
+	if (!(dir = opendir(basedir))) {
+		return NULL;
+	}
+
+	list_t *themes = create_list();
+	struct dirent *entry;
+	while ((entry = readdir(dir))) {
+		if (entry->d_name[0] == '.') continue;
+
+		struct icon_theme *theme = read_theme_file(basedir, entry->d_name);
+		if (theme) {
+			list_add(themes, theme);
+		}
+	}
+	return themes;
+}
+
+void init_themes(list_t **themes, list_t **basedirs) {
+	*basedirs = get_basedirs();
+
+	*themes = create_list();
+	for (int i = 0; i < (*basedirs)->length; ++i) {
+		list_t *dir_themes = load_themes_in_dir((*basedirs)->items[i]);
+		list_cat(*themes, dir_themes);
+		list_free(dir_themes);
+	}
+
+	list_t *theme_names = create_list();
+	for (int i = 0; i < (*themes)->length; ++i) {
+		struct icon_theme *theme = (*themes)->items[i];
+		list_add(theme_names, theme->name);
+	}
+	wlr_log(WLR_DEBUG, "Loaded themes: %s", join_list(theme_names, ", "));
+	list_free(theme_names);
+}
+
+void finish_themes(list_t *themes, list_t *basedirs) {
+	for (int i = 0; i < themes->length; ++i) {
+		destroy_theme(themes->items[i]);
+	}
+	list_free(themes);
+	list_free_items_and_destroy(basedirs);
+}
+
+static char *find_icon_in_subdir(char *name, char *basedir, char *theme,
+		char *subdir) {
+	static const char *extensions[] = {
+#if HAVE_GDK_PIXBUF
+		"svg",
+#endif
+		"png",
+#if HAVE_GDK_PIXBUF
+		"xpm"
+#endif
+	};
+
+	size_t path_len = snprintf(NULL, 0, "%s/%s/%s/%s.EXT", basedir, theme,
+			subdir, name) + 1;
+	char *path = malloc(path_len);
+
+	for (size_t i = 0; i < sizeof(extensions) / sizeof(*extensions); ++i) {
+		snprintf(path, path_len, "%s/%s/%s/%s.%s", basedir, theme, subdir,
+				name, extensions[i]);
+		if (access(path, R_OK) == 0) {
+			return path;
+		}
+	}
+
+	free(path);
+	return NULL;
+}
+
+static bool theme_exists_in_basedir(char *theme, char *basedir) {
+	size_t path_len = snprintf(NULL, 0, "%s/%s", basedir, theme) + 1;
+	char *path = malloc(path_len);
+	snprintf(path, path_len, "%s/%s", basedir, theme);
+	bool ret = dir_exists(path);
+	free(path);
+	return ret;
+}
+
+static char *find_icon_with_theme(list_t *basedirs, list_t *themes, char *name,
+		int size, char *theme_name, int *min_size, int *max_size) {
+	struct icon_theme *theme = NULL;
+	for (int i = 0; i < themes->length; ++i) {
+		theme = themes->items[i];
+		if (strcmp(theme->name, theme_name) == 0) {
+			break;
+		}
+		theme = NULL;
+	}
+	if (!theme) return NULL;
+
+	char *icon = NULL;
+	for (int i = 0; i < basedirs->length; ++i) {
+		if (!theme_exists_in_basedir(theme->dir, basedirs->items[i])) {
+			continue;
+		}
+		// search backwards to hopefully hit scalable/larger icons first
+		for (int j = theme->subdirs->length - 1; j >= 0; --j) {
+			struct icon_theme_subdir *subdir = theme->subdirs->items[j];
+			if (size >= subdir->min_size && size <= subdir->max_size) {
+				if ((icon = find_icon_in_subdir(name, basedirs->items[i],
+								theme->dir, subdir->name))) {
+					*min_size = subdir->min_size;
+					*max_size = subdir->max_size;
+					return icon;
+				}
+			}
+		}
+	}
+
+	// inexact match
+	unsigned smallest_error = -1; // UINT_MAX
+	for (int i = 0; i < basedirs->length; ++i) {
+		if (!theme_exists_in_basedir(theme->dir, basedirs->items[i])) {
+			continue;
+		}
+		for (int j = theme->subdirs->length - 1; j >= 0; --j) {
+			struct icon_theme_subdir *subdir = theme->subdirs->items[j];
+			unsigned error = (size > subdir->max_size ? size - subdir->max_size : 0)
+				+ (size < subdir->min_size ? subdir->min_size - size : 0);
+			if (error < smallest_error) {
+				char *test_icon = find_icon_in_subdir(name, basedirs->items[i],
+						theme->dir, subdir->name);
+				if (test_icon) {
+					icon = test_icon;
+					smallest_error = error;
+					*min_size = subdir->min_size;
+					*max_size = subdir->max_size;
+				}
+			}
+		}
+	}
+
+	if (!icon && theme->inherits) {
+		icon = find_icon_with_theme(basedirs, themes, name, size,
+				theme->inherits, min_size, max_size);
+	}
+
+	return icon;
+}
+
+char *find_icon_in_dir(char *name, char *dir, int *min_size, int *max_size) {
+	char *icon = find_icon_in_subdir(name, dir, "", "");
+	if (icon) {
+		*min_size = 1;
+		*max_size = 512;
+	}
+	return icon;
+
+}
+
+static char *find_fallback_icon(list_t *basedirs, char *name, int *min_size,
+		int *max_size) {
+	for (int i = 0; i < basedirs->length; ++i) {
+		char *icon = find_icon_in_dir(name, basedirs->items[i], min_size, max_size);
+		if (icon) {
+			return icon;
+		}
+	}
+	return NULL;
+}
+
+char *find_icon(list_t *themes, list_t *basedirs, char *name, int size,
+		char *theme, int *min_size, int *max_size) {
+	// TODO https://specifications.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html#implementation_notes
+	char *icon = NULL;
+	if (theme) {
+		icon = find_icon_with_theme(basedirs, themes, name, size, theme,
+				min_size, max_size);
+	}
+	if (!icon) {
+		icon = find_icon_with_theme(basedirs, themes, name, size, "Hicolor",
+				min_size, max_size);
+	}
+	if (!icon) {
+		icon = find_fallback_icon(basedirs, name, min_size, max_size);
+	}
+	return icon;
+}
diff --git a/swaybar/tray/tray.c b/swaybar/tray/tray.c
index 36ee3c30..c1d3b50b 100644
--- a/swaybar/tray/tray.c
+++ b/swaybar/tray/tray.c
@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "swaybar/bar.h"
+#include "swaybar/tray/icon.h"
 #include "swaybar/tray/tray.h"
 #include "swaybar/tray/watcher.h"
 #include "log.h"
@@ -28,6 +29,8 @@ struct swaybar_tray *create_tray(struct swaybar *bar) {
 	tray->watcher_xdg = create_watcher("freedesktop", tray->bus);
 	tray->watcher_kde = create_watcher("kde", tray->bus);
 
+	init_themes(&tray->themes, &tray->basedirs);
+
 	return tray;
 }
 
@@ -38,6 +41,7 @@ void destroy_tray(struct swaybar_tray *tray) {
 	destroy_watcher(tray->watcher_xdg);
 	destroy_watcher(tray->watcher_kde);
 	sd_bus_flush_close_unref(tray->bus);
+	finish_themes(tray->themes, tray->basedirs);
 	free(tray);
 }