diff --git a/chrome/content/zotero/xpcom/data/cachedTypes.js b/chrome/content/zotero/xpcom/data/cachedTypes.js
index f8b472973..76ddfed44 100644
--- a/chrome/content/zotero/xpcom/data/cachedTypes.js
+++ b/chrome/content/zotero/xpcom/data/cachedTypes.js
@@ -558,6 +558,133 @@ Zotero.CharacterSets = new function() {
 			+ "(SELECT " + this._idCol + " FROM itemAttachments)";
 		return Zotero.DB.queryAsync(sql);
 	};
+	
+	// Converts charset label to charset name
+	// https://encoding.spec.whatwg.org/#names-and-labels
+	// @param {String} charset
+	// @return {String|Boolean} Normalized charset name or FALSE if not recognized
+	this.toCanonical = function (charset) {
+		let canonical = charsetMap[charset.trim().toLowerCase()];
+		if (!canonical) {
+			Zotero.debug("Unrecognized charset: " + charset);
+			return false;
+		}
+		return canonical;
+	};
+	
+	// Normalizes charset label to conform to DOM standards
+	// https://dom.spec.whatwg.org/#dom-document-characterset
+	// @param {String} charset
+	// @param {Boolean} mozCompat Whether to return a Mozilla-compatible label
+	//   for use in Gecko internal APIs.
+	//   https://developer.mozilla.org/en-US/docs/Gecko/Character_sets_supported_by_Gecko
+	// @return {String|Boolean} Normalized label or FALSE is not recognized
+	this.toLabel = function (charset, mozCompat) {
+		charset = this.toCanonical(charset);
+		if (!charset) return false;
+		
+		if (mozCompat && charset == 'gbk') return charset; // See https://developer.mozilla.org/en-US/docs/Gecko/Character_sets_supported_by_Gecko
+		
+		return compatibilityNames[charset];
+	}
+	
+	// From https://encoding.spec.whatwg.org/#names-and-labels
+	// Don't use this, use charsetMap. See below
+	let charsetList = {
+		"utf-8": ["unicode-1-1-utf-8", "utf-8", "utf8"],
+		"ibm866": ["866", "cp866", "csibm866", "ibm866"],
+		"iso-8859-2": ["csisolatin2", "iso-8859-2", "iso-ir-101", "iso8859-2", "iso88592", "iso_8859-2", 
+			"iso_8859-2:1987","l2", "latin2"],
+		"iso-8859-3": ["csisolatin3", "iso-8859-3", "iso-ir-109", "iso8859-3", "iso88593", "iso_8859-3", 
+			"iso_8859-3:1988","l3", "latin3"],
+		"iso-8859-4": ["csisolatin4", "iso-8859-4", "iso-ir-110", "iso8859-4", "iso88594", "iso_8859-4", 
+			"iso_8859-4:1988","l4", "latin4"],
+		"iso-8859-5": ["csisolatincyrillic", "cyrillic", "iso-8859-5", "iso-ir-144", "iso8859-5", "iso88595", "iso_8859-5", 
+			"iso_8859-5:1988"],
+		"iso-8859-6": ["arabic", "asmo-708", "csiso88596e", "csiso88596i", "csisolatinarabic", "ecma-114", "iso-8859-6", "iso-8859-6-e", "iso-8859-6-i", "iso-ir-127", "iso8859-6", "iso88596", "iso_8859-6", 
+			"iso_8859-6:1987"],
+		"iso-8859-7": ["csisolatingreek", "ecma-118", "elot_928", "greek", "greek8", "iso-8859-7", "iso-ir-126", "iso8859-7", "iso88597", "iso_8859-7", 
+			"iso_8859-7:1987","sun_eu_greek"],
+		"iso-8859-8": ["csiso88598e", "csisolatinhebrew", "hebrew", "iso-8859-8", "iso-8859-8-e", "iso-ir-138", "iso8859-8", "iso88598", "iso_8859-8", 
+			"iso_8859-8:1988","visual"],
+		"iso-8859-8-i": ["csiso88598i", "iso-8859-8-i", "logical"],
+		"iso-8859-10": ["csisolatin6", "iso-8859-10", "iso-ir-157", "iso8859-10", "iso885910", "l6", "latin6"],
+		"iso-8859-13": ["iso-8859-13", "iso8859-13", "iso885913"],
+		"iso-8859-14": ["iso-8859-14", "iso8859-14", "iso885914"],
+		"iso-8859-15": ["csisolatin9", "iso-8859-15", "iso8859-15", "iso885915", "iso_8859-15", "l9"],
+		"iso-8859-16": ["iso-8859-16"],
+		"koi8-r": ["cskoi8r", "koi", "koi8", "koi8-r", "koi8_r"],
+		"koi8-u": ["koi8-u"],
+		"macintosh": ["csmacintosh", "mac", "macintosh", "x-mac-roman"],
+		"windows-874": ["dos-874", "iso-8859-11", "iso8859-11", "iso885911", "tis-620", "windows-874"],
+		"windows-1250": ["cp1250", "windows-1250", "x-cp1250"],
+		"windows-1251": ["cp1251", "windows-1251", "x-cp1251"],
+		"windows-1252": [
+			"ansi_x3.4-1968","ascii", "cp1252", "cp819", "csisolatin1", "ibm819", "iso-8859-1", "iso-ir-100", "iso8859-1", "iso88591", "iso_8859-1", 
+			"iso_8859-1:1987","l1", "latin1", "us-ascii", "windows-1252", "x-cp1252"],
+		"windows-1253": ["cp1253", "windows-1253", "x-cp1253"],
+		"windows-1254": ["cp1254", "csisolatin5", "iso-8859-9", "iso-ir-148", "iso8859-9", "iso88599", "iso_8859-9", 
+			"iso_8859-9:1989","l5", "latin5", "windows-1254", "x-cp1254"],
+		"windows-1255": ["cp1255", "windows-1255", "x-cp1255"],
+		"windows-1256": ["cp1256", "windows-1256", "x-cp1256"],
+		"windows-1257": ["cp1257", "windows-1257", "x-cp1257"],
+		"windows-1258": ["cp1258", "windows-1258", "x-cp1258"],
+		"x-mac-cyrillic": ["x-mac-cyrillic", "x-mac-ukrainian"],
+		"gbk": ["chinese", "csgb2312", "csiso58gb231280", "gb2312", "gb_2312", "gb_2312-80", "gbk", "iso-ir-58", "x-gbk"],
+		"gb18030": ["gb18030"],
+		"big5": ["big5", "cn-big5", "csbig5", "x-x-big5"],
+		"big5-hkscs": ["big5-hkscs"], // see https://bugzilla.mozilla.org/show_bug.cgi?id=912470
+		"euc-jp": ["cseucpkdfmtjapanese", "euc-jp", "x-euc-jp"],
+		"iso-2022-jp": ["csiso2022jp", "iso-2022-jp"],
+		"shift_jis": ["csshiftjis", "ms_kanji", "shift-jis", "shift_jis", "sjis", "windows-31j", "x-sjis"],
+		"euc-kr": ["cseuckr", "csksc56011987", "euc-kr", "iso-ir-149", "korean", "ks_c_5601-1987", "ks_c_5601-1989", "ksc5601", "ksc_5601", "windows-949"],
+		"replacement": ["csiso2022kr", "hz-gb-2312", "iso-2022-cn", "iso-2022-cn-ext", "iso-2022-kr"],
+		"utf-16be": ["utf-16be"],
+		"utf-16le": ["utf-16", "utf-16le"],
+		"x-user-defined": ["x-user-defined"]
+	}
+	
+	// As per https://dom.spec.whatwg.org/#dom-document-characterset
+	let compatibilityNames = {
+		"utf-8": "UTF-8",
+		"ibm866": "IBM866",
+		"iso-8859-2": "ISO-8859-2",
+		"iso-8859-3": "ISO-8859-3",
+		"iso-8859-4": "ISO-8859-4",
+		"iso-8859-5": "ISO-8859-5",
+		"iso-8859-6": "ISO-8859-6",
+		"iso-8859-7": "ISO-8859-7",
+		"iso-8859-8": "ISO-8859-8",
+		"iso-8859-8-i": "ISO-8859-8-I",
+		"iso-8859-10": "ISO-8859-10",
+		"iso-8859-13": "ISO-8859-13",
+		"iso-8859-14": "ISO-8859-14",
+		"iso-8859-15": "ISO-8859-15",
+		"iso-8859-16": "ISO-8859-16",
+		"koi8-r": "KOI8-R",
+		"koi8-u": "KOI8-U",
+		"gbk": "GBK",
+		"big5": "Big5",
+		"euc-jp": "EUC-JP",
+		"iso-2022-jp": "ISO-2022-JP",
+		"shift_jis": "Shift_JIS",
+		"euc-kr": "EUC-KR",
+		"utf-16be": "UTF-16BE",
+		"utf-16le": "UTF-16LE"
+	};
+	
+	let charsetMap = {};
+	for (let canonical in charsetList) {
+		charsetMap[canonical.toLowerCase()] = canonical;
+		charsetList[canonical].forEach((c) => charsetMap[c.toLowerCase()] = canonical);
+		
+		if (!compatibilityNames[canonical]) {
+			compatibilityNames[canonical] = canonical;
+		}
+	}
+	
+	// Clear charsetList
+	charsetList = null;
 }
 
 
diff --git a/test/tests/cachedTypesTest.js b/test/tests/cachedTypesTest.js
new file mode 100644
index 000000000..9da4fdbee
--- /dev/null
+++ b/test/tests/cachedTypesTest.js
@@ -0,0 +1,38 @@
+describe("Zotero.CachedTypes", function() {
+	describe("Zotero.CharacterSets", function() {
+		describe("#toCanonical()", function() {
+			let toCanon = Zotero.CharacterSets.toCanonical.bind(Zotero.CharacterSets);
+			it("should return charset name given a normalized charset name", function() {
+				assert.equal(toCanon('utf-8'), 'utf-8');
+				assert.equal(toCanon('windows-1252'), 'windows-1252');
+				assert.equal(toCanon('utf-16be'), 'utf-16be')
+			});
+			it("should return charset name given a label", function() {
+				assert.equal(toCanon('unicode-1-1-utf-8'), 'utf-8');
+				assert.equal(toCanon('ISO-8859-16'), 'iso-8859-16', 'converts compatibility label to name');
+				assert.equal(toCanon('Chinese'), 'gbk', 'not case sensitive');
+				assert.equal(toCanon('\ncp1252 '), 'windows-1252', 'ignores leading/trailing whitespace');
+			});
+			it("should return big5-hkscs for big5-hkscs", function() {
+				assert.equal(toCanon('big5-hkscs'), 'big5-hkscs');
+			});
+			it("should return false for invalid charset", function() {
+				assert.isFalse(toCanon('foo'));
+			});
+		});
+		describe("#toLabel()", function() {
+			let toLabel = Zotero.CharacterSets.toLabel.bind(Zotero.CharacterSets);
+			it("should return a compatibility label given a charset name", function() {
+				assert.equal(toLabel('utf-8'), 'UTF-8');
+				assert.equal(toLabel('gbk'), 'GBK', 'returns GBK in non-mozCompat mode');
+				assert.equal(toLabel('macintosh'), 'macintosh', 'unspecified compatibility mappings are unchanged');
+			});
+			it("should return gbk in mozCompat mode", function() {
+				assert.equal(toLabel('gbk', true), 'gbk');
+			});
+			it("should return false for invalid charset", function() {
+				assert.isFalse(toLabel('foo'));
+			});
+		});
+	});
+});
\ No newline at end of file