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Here are some common errors and their resolutions. This is not comprehensive. The issue tracker has a wealth of information and user-contributed examples.

If issues are not covered in the docs or the issue tracker, or if a solution is not discussed in the documentation, we would appreciate a bug report.

Special Thanks

Special thanks to the early adopters and users for discovering and sharing many workarounds and solutions!


SCRIPT5022: DataCloneError

IE10 does not properly support Transferable.

Object doesn't support property or method 'slice'

IE does not implement Uint8Array#slice. An implementation is included in the shim script. Check the "Standalone" Installation note

TypeError: f.substr is not a function

Some Google systems use the base64url encoding. base64url and base64 are different encodings. A simple regular expression can translate the data:

var wb =, "/").replace(/-/g, "+"), {type:'base64'});

Error: Cannot read property '0' of undefined

FileReader#readAsText will corrupt binary data including XLSX, XLSB, XLS, and other binary spreadsheet files.

Applications should use FileReader#readAsArrayBuffer or Blob#arrayBuffer. Examples are included in "User Submissions"

Applications specifically targeting legacy browsers like IE10 should use FileReader#readAsBinaryString to read the data and call using the binary type.

Unsupported file undefined when reading ArrayBuffer objects

Old versions of the library did not automatically detect ArrayBuffer objects.

Workaround (click to show)
Legacy workaround

This solution is not recommended for production deployments. Native support for ArrayBuffer was added in library version 0.9.9.

After reading data with FileReader#readAsArrayBuffer, manually translate to binary string and call with type "binary"

document.getElementById('file-object').addEventListener("change", function(e) {
var files =,file;
if (!files || files.length == 0) return;
file = files[0];
var fileReader = new FileReader();
fileReader.onload = function (e) {
var filename =;
// pre-process data
var binary = "";
var bytes = new Uint8Array(;
var length = bytes.byteLength;
for (var i = 0; i < length; i++) {
binary += String.fromCharCode(bytes[i]);
// call 'xlsx' to read the file
var oFile =, {type: 'binary', cellDates:true, cellStyles:true});

Data Issues

CSV and XLS files with Chinese or Japanese characters look garbled

The ESM build, used in tools like Webpack and in Deno, does not include the codepage tables by default. The "Frameworks and Bundlers" section explains how to load support.

DBF files with Chinese or Japanese characters have underscores

As mentioned in the previous answer, codepage tables must be loaded.

When reading legacy files that do not include character set metadata, the codepage option controls the codepage. Common values:

874Windows Thai
932Japanese Shift-JIS
936Simplified Chinese GBK
950Traditional Chinese Big5
1200UTF-16 Little Endian
1252Windows Latin 1

When writing files in legacy formats like DBF, the default codepage 1252 will be used. The codepage option will override the setting. Any characters missing from the character set will be replaced with underscores.

Worksheet only includes one row of data

Some third-party writer tools will not update the dimensions records in XLSX or XLS or XLSB exports. SheetJS utility functions will skip values not in range.

The following helper function will recalculate the range:

function update_sheet_range(ws) {
var range = {s:{r:Infinity, c:Infinity},e:{r:0,c:0}};
Object.keys(ws).filter(function(x) { return x.charAt(0) != "!"; }).map(XLSX.utils.decode_cell).forEach(function(x) {
range.s.c = Math.min(range.s.c, x.c); range.s.r = Math.min(range.s.r, x.r);
range.e.c = Math.max(range.e.c, x.c); range.e.r = Math.max(range.e.r, x.r);
ws['!ref'] = XLSX.utils.encode_range(range);
More Code Snippets (click to show)

set_sheet_range changes a sheet's range given a general target spec that can include only the start or end cell:

/* given the old range and a new range spec, produce the new range */
function change_range(old, range) {
var oldrng = XLSX.utils.decode_range(old), newrng;
if(typeof range == "string") {
if(range.charAt(0) == ":") newrng = {e:XLSX.utils.decode_cell(range.substr(1))};
else if(range.charAt(range.length - 1) == ":") newrng = {s:XLSX.utils.decode_cell(range.substr(0, range.length - 1))};
else newrng = XLSX.utils.decode_range(range);
} else newrng = range;
if(newrng.s) {
if(newrng.s.c != null) oldrng.s.c = newrng.s.c;
if(newrng.s.r != null) oldrng.s.r = newrng.s.r;
if(newrng.e) {
if(newrng.e.c != null) oldrng.e.c = newrng.e.c;
if(newrng.e.r != null) oldrng.e.r = newrng.e.r;

return XLSX.utils.encode_range(oldrng);

/* call change_sheet and modify worksheet */
function set_sheet_range(sheet, range) {
sheet['!ref'] = change_range(sheet['!ref'], range);

Adding a cell to a range

function range_add_cell(range, cell) {
var rng = XLSX.utils.decode_range(range);
var c = typeof cell == 'string' ? XLSX.utils.decode_cell(cell) : cell;
if(rng.s.r > c.r) rng.s.r = c.r;
if(rng.s.c > c.c) rng.s.c = c.c;

if(rng.e.r < c.r) rng.e.r = c.r;
if(rng.e.c < c.c) rng.e.c = c.c;
return XLSX.utils.encode_range(rng);

function add_to_sheet(sheet, cell) {
sheet['!ref'] = range_add_cell(sheet['!ref'], cell);