diff --git a/Makefile b/Makefile
index 47df70a..f3d8918 100644
--- a/Makefile
+++ b/Makefile
@@ -12,10 +12,13 @@ FLOWTARGET=$(LIB).flow.js
 FLOWTGTS=$(TARGET) $(AUXTARGETS)
 CLOSURE=/usr/local/lib/node_modules/google-closure-compiler/compiler.jar
 
+ESMJSTGT=crc32.mjs
+ESMJSDEPS=$(shell cat misc/mjs.lst)
+
 ## Main Targets
 
 .PHONY: all
-all: $(TARGET) $(AUXTARGETS) ## Build library and auxiliary scripts
+all: $(TARGET) $(AUXTARGETS) $(ESMJSTGT) crc32c.mjs ## Build library and auxiliary scripts
 
 $(FLOWTGTS): %.js : %.flow.js
 	node -e 'process.stdout.write(require("fs").readFileSync("$<","utf8").replace(/^[ \t]*\/\*[:#][^*]*\*\/\s*(\n)?/gm,"").replace(/\/\*[:#][^*]*\*\//gm,""))' > $@
@@ -23,6 +26,9 @@ $(FLOWTGTS): %.js : %.flow.js
 $(FLOWTARGET): $(DEPS)
 	cat $^ | tr -d '\15\32' > $@
 
+$(ESMJSTGT): $(ESMJSDEPS)
+	cat $^ | tr -d '\15\32' > $@
+
 bits/01_version.js: package.json
 	echo "$(ULIB).version = '"`grep version package.json | awk '{gsub(/[^0-9a-z\.-]/,"",$$2); print $$2}'`"';" > $@
 
@@ -33,6 +39,9 @@ clean: clean-baseline ## Remove targets and build artifacts
 crc32c.flow.js: crc32.flow.js
 	cat $^ | sed 's/-306674912/-2097792136/g; s/CRC32\([ \/\.]\)/CRC32C\1/g' > $@
 
+crc32c.mjs: crc32.mjs
+	cat $^ | sed 's/-306674912/-2097792136/g; s/CRC32\([ \/\.]\)/CRC32C\1/g' > $@
+
 ## Testing
 
 .PHONY: test mocha
diff --git a/README.md b/README.md
index 43ecf2f..bbff3d9 100644
--- a/README.md
+++ b/README.md
@@ -28,12 +28,18 @@ checksum for a specified file or standard input.
 
 ## Integration
 
-Using NodeJS or a bundler:
+Using NodeJS or a bundler with `require`:
 
 ```js
 var CRC32 = require("crc-32");
 ```
 
+Using NodeJS or a bundler with `import`:
+
+```js
+import { bstr, buf, str } from "crc-32";
+```
+
 In the browser, the `crc32.js` script can be loaded directly:
 
 ```html
@@ -55,6 +61,12 @@ Using NodeJS or a bundler:
 var CRC32C = require("crc-32/crc32c");
 ```
 
+Using NodeJS or a bundler with `import`:
+
+```js
+import { bstr, buf, str } from "crc-32/crc32c";
+```
+
 In the browser, the `crc32c.js` script can be loaded directly:
 
 ```html
@@ -71,7 +83,7 @@ desirable.  To prevent the behavior, define `DO_NOT_EXPORT_CRC`.
 In all cases, the relevant function takes an argument representing data and an
 optional second argument representing the starting "seed" (for rolling CRC).
 
-The return value is a signed 32-bit integer.
+**The return value is a signed 32-bit integer!**
 
 - `CRC32.buf(byte array or buffer[, seed])` assumes the argument is a sequence
   of 8-bit unsigned integers (nodejs `Buffer`, `Uint8Array` or array of bytes).
@@ -130,6 +142,25 @@ crc32 = CRC32.buf(Buffer.from(bstr, "binary"), 0);
 This does not apply to browser `Buffer` shims, and thus is not implemented in
 the library directly.
 
+### Signed Integers
+
+Unconventional for a CRC32 checksum, this library uses signed 32-bit integers.
+This is for performance reasons.  Standard JS operators can convert between
+signed and unsigned 32-bit integers:
+
+```js
+CRC32.str("SheetJS")                            // -1647298270 (signed)
+CRC32.str("SheetJS") >>> 0                      //  2647669026 (unsigned)
+(CRC32.str("SheetJS")>>>0).toString(16)         //  "9dd03922" (hex)
+
+(2647669026 | 0)                                // -1647298270
+```
+
+- `x >>> 0` converts a number value to unsigned 32-bit integer.
+
+- `x | 0` converts a number value to signed 32-bit integer.
+
+
 ## Testing
 
 `make test` will run the nodejs-based test.
diff --git a/crc32.mjs b/crc32.mjs
new file mode 100644
index 0000000..a10f230
--- /dev/null
+++ b/crc32.mjs
@@ -0,0 +1,95 @@
+/*! crc32.js (C) 2014-present SheetJS -- http://sheetjs.com */
+/* vim: set ts=2: */
+var CRC32 = {};
+CRC32.version = '1.2.2';
+/*::
+type CRC32Type = number;
+type ABuf = Array<number> | Buffer | Uint8Array;
+type CRC32TableType = Array<number> | Int32Array;
+*/
+/*global Int32Array */
+function signed_crc_table()/*:CRC32TableType*/ {
+	var c = 0, table/*:Array<number>*/ = new Array(256);
+
+	for(var n =0; n != 256; ++n){
+		c = n;
+		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+		table[n] = c;
+	}
+
+	return typeof Int32Array !== 'undefined' ? new Int32Array(table) : table;
+}
+
+var T0 = signed_crc_table();
+function slice_by_16_tables(T) {
+	var c = 0, v = 0, n = 0, table/*:Array<number>*/ = typeof Int32Array !== 'undefined' ? new Int32Array(4096) : new Array(4096) ;
+
+	for(n = 0; n != 256; ++n) table[n] = T[n];
+	for(n = 0; n != 256; ++n) {
+		v = T[n];
+		for(c = 256 + n; c < 4096; c += 256) v = table[c] = (v >>> 8) ^ T[v & 0xFF];
+	}
+	var out = [];
+	for(n = 1; n != 16; ++n) out[n - 1] = typeof Int32Array !== 'undefined' ? table.subarray(n * 256, n * 256 + 256) : table.slice(n * 256, n * 256 + 256);
+	return out;
+}
+var TT = slice_by_16_tables(T0);
+var T1 = TT[0],  T2 = TT[1],  T3 = TT[2],  T4 = TT[3],  T5 = TT[4];
+var T6 = TT[5],  T7 = TT[6],  T8 = TT[7],  T9 = TT[8],  Ta = TT[9];
+var Tb = TT[10], Tc = TT[11], Td = TT[12], Te = TT[13], Tf = TT[14];
+function crc32_bstr(bstr/*:string*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
+	var C = seed/*:: ? 0 : 0 */ ^ -1;
+	for(var i = 0, L = bstr.length; i < L;) C = (C>>>8) ^ T0[(C^bstr.charCodeAt(i++))&0xFF];
+	return ~C;
+}
+
+function crc32_buf(B/*:ABuf*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
+	var C = seed/*:: ? 0 : 0 */ ^ -1, L = B.length - 15, i = 0;
+	for(; i < L;) C =
+		Tf[B[i++] ^ (C & 255)] ^
+		Te[B[i++] ^ ((C >> 8) & 255)] ^
+		Td[B[i++] ^ ((C >> 16) & 255)] ^
+		Tc[B[i++] ^ (C >>> 24)] ^
+		Tb[B[i++]] ^ Ta[B[i++]] ^ T9[B[i++]] ^ T8[B[i++]] ^
+		T7[B[i++]] ^ T6[B[i++]] ^ T5[B[i++]] ^ T4[B[i++]] ^
+		T3[B[i++]] ^ T2[B[i++]] ^ T1[B[i++]] ^ T0[B[i++]];
+	L += 15;
+	while(i < L) C = (C>>>8) ^ T0[(C^B[i++])&0xFF];
+	return ~C;
+}
+
+function crc32_str(str/*:string*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
+	var C = seed/*:: ? 0 : 0 */ ^ -1;
+	for(var i = 0, L = str.length, c = 0, d = 0; i < L;) {
+		c = str.charCodeAt(i++);
+		if(c < 0x80) {
+			C = (C>>>8) ^ T0[(C^c)&0xFF];
+		} else if(c < 0x800) {
+			C = (C>>>8) ^ T0[(C ^ (192|((c>>6)&31)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|(c&63)))&0xFF];
+		} else if(c >= 0xD800 && c < 0xE000) {
+			c = (c&1023)+64; d = str.charCodeAt(i++)&1023;
+			C = (C>>>8) ^ T0[(C ^ (240|((c>>8)&7)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|((c>>2)&63)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|((d>>6)&15)|((c&3)<<4)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|(d&63)))&0xFF];
+		} else {
+			C = (C>>>8) ^ T0[(C ^ (224|((c>>12)&15)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|((c>>6)&63)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|(c&63)))&0xFF];
+		}
+	}
+	return ~C;
+}
+export const version = CRC32.version;
+export const table = T0;
+export const bstr = crc32_bstr;
+export const buf = crc32_buf;
+export const str = crc32_str;
diff --git a/crc32c.mjs b/crc32c.mjs
new file mode 100644
index 0000000..8316f62
--- /dev/null
+++ b/crc32c.mjs
@@ -0,0 +1,95 @@
+/*! crc32.js (C) 2014-present SheetJS -- http://sheetjs.com */
+/* vim: set ts=2: */
+var CRC32C = {};
+CRC32C.version = '1.2.2';
+/*::
+type CRC32Type = number;
+type ABuf = Array<number> | Buffer | Uint8Array;
+type CRC32TableType = Array<number> | Int32Array;
+*/
+/*global Int32Array */
+function signed_crc_table()/*:CRC32TableType*/ {
+	var c = 0, table/*:Array<number>*/ = new Array(256);
+
+	for(var n =0; n != 256; ++n){
+		c = n;
+		c = ((c&1) ? (-2097792136 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-2097792136 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-2097792136 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-2097792136 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-2097792136 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-2097792136 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-2097792136 ^ (c >>> 1)) : (c >>> 1));
+		c = ((c&1) ? (-2097792136 ^ (c >>> 1)) : (c >>> 1));
+		table[n] = c;
+	}
+
+	return typeof Int32Array !== 'undefined' ? new Int32Array(table) : table;
+}
+
+var T0 = signed_crc_table();
+function slice_by_16_tables(T) {
+	var c = 0, v = 0, n = 0, table/*:Array<number>*/ = typeof Int32Array !== 'undefined' ? new Int32Array(4096) : new Array(4096) ;
+
+	for(n = 0; n != 256; ++n) table[n] = T[n];
+	for(n = 0; n != 256; ++n) {
+		v = T[n];
+		for(c = 256 + n; c < 4096; c += 256) v = table[c] = (v >>> 8) ^ T[v & 0xFF];
+	}
+	var out = [];
+	for(n = 1; n != 16; ++n) out[n - 1] = typeof Int32Array !== 'undefined' ? table.subarray(n * 256, n * 256 + 256) : table.slice(n * 256, n * 256 + 256);
+	return out;
+}
+var TT = slice_by_16_tables(T0);
+var T1 = TT[0],  T2 = TT[1],  T3 = TT[2],  T4 = TT[3],  T5 = TT[4];
+var T6 = TT[5],  T7 = TT[6],  T8 = TT[7],  T9 = TT[8],  Ta = TT[9];
+var Tb = TT[10], Tc = TT[11], Td = TT[12], Te = TT[13], Tf = TT[14];
+function crc32_bstr(bstr/*:string*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
+	var C = seed/*:: ? 0 : 0 */ ^ -1;
+	for(var i = 0, L = bstr.length; i < L;) C = (C>>>8) ^ T0[(C^bstr.charCodeAt(i++))&0xFF];
+	return ~C;
+}
+
+function crc32_buf(B/*:ABuf*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
+	var C = seed/*:: ? 0 : 0 */ ^ -1, L = B.length - 15, i = 0;
+	for(; i < L;) C =
+		Tf[B[i++] ^ (C & 255)] ^
+		Te[B[i++] ^ ((C >> 8) & 255)] ^
+		Td[B[i++] ^ ((C >> 16) & 255)] ^
+		Tc[B[i++] ^ (C >>> 24)] ^
+		Tb[B[i++]] ^ Ta[B[i++]] ^ T9[B[i++]] ^ T8[B[i++]] ^
+		T7[B[i++]] ^ T6[B[i++]] ^ T5[B[i++]] ^ T4[B[i++]] ^
+		T3[B[i++]] ^ T2[B[i++]] ^ T1[B[i++]] ^ T0[B[i++]];
+	L += 15;
+	while(i < L) C = (C>>>8) ^ T0[(C^B[i++])&0xFF];
+	return ~C;
+}
+
+function crc32_str(str/*:string*/, seed/*:?CRC32Type*/)/*:CRC32Type*/ {
+	var C = seed/*:: ? 0 : 0 */ ^ -1;
+	for(var i = 0, L = str.length, c = 0, d = 0; i < L;) {
+		c = str.charCodeAt(i++);
+		if(c < 0x80) {
+			C = (C>>>8) ^ T0[(C^c)&0xFF];
+		} else if(c < 0x800) {
+			C = (C>>>8) ^ T0[(C ^ (192|((c>>6)&31)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|(c&63)))&0xFF];
+		} else if(c >= 0xD800 && c < 0xE000) {
+			c = (c&1023)+64; d = str.charCodeAt(i++)&1023;
+			C = (C>>>8) ^ T0[(C ^ (240|((c>>8)&7)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|((c>>2)&63)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|((d>>6)&15)|((c&3)<<4)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|(d&63)))&0xFF];
+		} else {
+			C = (C>>>8) ^ T0[(C ^ (224|((c>>12)&15)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|((c>>6)&63)))&0xFF];
+			C = (C>>>8) ^ T0[(C ^ (128|(c&63)))&0xFF];
+		}
+	}
+	return ~C;
+}
+export const version = CRC32C.version;
+export const table = T0;
+export const bstr = crc32_bstr;
+export const buf = crc32_buf;
+export const str = crc32_str;
diff --git a/misc/00_header.js b/misc/00_header.js
new file mode 100644
index 0000000..a172cbd
--- /dev/null
+++ b/misc/00_header.js
@@ -0,0 +1,3 @@
+/*! crc32.js (C) 2014-present SheetJS -- http://sheetjs.com */
+/* vim: set ts=2: */
+var CRC32 = {};
diff --git a/misc/99_footer.js b/misc/99_footer.js
new file mode 100644
index 0000000..0f3318d
--- /dev/null
+++ b/misc/99_footer.js
@@ -0,0 +1,5 @@
+export const version = CRC32.version;
+export const table = T0;
+export const bstr = crc32_bstr;
+export const buf = crc32_buf;
+export const str = crc32_str;
diff --git a/misc/mjs.lst b/misc/mjs.lst
new file mode 100644
index 0000000..697323e
--- /dev/null
+++ b/misc/mjs.lst
@@ -0,0 +1,6 @@
+misc/00_header.js
+bits/01_version.js
+bits/10_types.js
+bits/20_crctable.js
+bits/40_crc.js
+misc/99_footer.js
diff --git a/package.json b/package.json
index a523291..14bdd82 100644
--- a/package.json
+++ b/package.json
@@ -8,8 +8,25 @@
 		"crc32": "bin/crc32.njs"
 	},
 	"main": "crc32.js",
+	"module": "crc32.mjs",
 	"types": "types/index.d.ts",
 	"typesVersions": { "*": { "*": ["types/index.d.ts" ] } },
+	"exports": {
+		".": {
+			"import": "./crc32.mjs",
+			"require": "./crc32.js"
+		},
+		"./crc32c": {
+			"import": "./crc32c.mjs",
+			"require": "./crc32c.js"
+		},
+		"./crc32.mjs": {
+			"import": "./crc32.mjs"
+		},
+		"./crc32c.mjs": {
+			"import": "./crc32c.mjs"
+		}
+	},
 	"dependencies": {
 	},
 	"devDependencies": {
@@ -36,7 +53,7 @@
 		}
 	},
 	"homepage": "https://sheetjs.com/",
-	"files": ["crc32.js", "crc32c.js", "bin/crc32.njs", "LICENSE", "README.md", "types/index.d.ts", "types/*.json"],
+	"files": ["crc32.js", "crc32c.js", "crc32.mjs", "crc32c.mjs", "bin/crc32.njs", "LICENSE", "README.md", "types/index.d.ts", "types/*.json"],
 	"bugs": { "url": "https://github.com/SheetJS/js-crc32/issues" },
 	"license": "Apache-2.0",
 	"engines": { "node": ">=0.8" }