PHPOffice/PhpSpreadsheet · error · ReaderException

$filename is an Invalid Spreadsheet file.

Error message

$filename is an Invalid Spreadsheet file.

What it means

Before parsing, the Csv reader runs its canRead() heuristic (recognizable delimiter structure such as commas/semicolons/tabs across lines). openFileOrMemory() throws this exception when that sniff fails, i.e. the content does not look like delimited text at all.

Solutions

1. Detect the real format first with IOFactory::identify($file) and instantiate the matching reader
2. If the file really is CSV, inspect it: ensure it contains recognizable delimiter lines and decodable text; re-export from the source system if corrupt
3. For non-standard delimiters, configure the Csv reader's delimiter settings before loading so the content is parsed as intended

Example fix

// before
$spreadsheet = (new Csv())->load($uploadPath); // upload is actually xlsx renamed .csv -> throws

// after
$type = IOFactory::identify($uploadPath);
$reader = IOFactory::createReader($type);
$spreadsheet = $reader->load($uploadPath);

$reader = new Csv();
if (!$reader->canRead($uploadPath)) {
    throw new RuntimeException('File does not look like a delimited CSV');
}
$spreadsheet = $reader->load($uploadPath);

try {
    $spreadsheet = (new Csv())->load($path);
} catch (ReaderException $e) {
    if (str_contains($e->getMessage(), 'Invalid Spreadsheet file')) {
        $spreadsheet = IOFactory::load($path); // retry with the detected real reader
    } else {
        throw $e;
    }
}

When it happens

Trigger: (new Csv())->load('notes.txt') where the file has no delimiter lines; binary content or a real .xlsx/.ods renamed to .csv; a single-column file with no delimiters anywhere; content garbled by wrong encoding so delimiter detection fails.

Common situations: User uploads where the original spreadsheet was merely renamed to .csv; automated imports pulling from endpoints that returned HTML error pages or JSON instead of CSV; ERP exports with unusual delimiters never configured on the reader.

Related errors

• is an invalid Gnumeric file.
• is an Invalid HTML file.
• is an Invalid SYLK file.
• Could not open file for reading.
• Could not open file $filename for reading.

AI-assisted analysis of PHPOffice/PhpSpreadsheet@65b080eef4 (2026-08-17). Data as JSON: /api/errors/17feba5023b312ff. Report an issue: GitHub.

Appendix: source

Thrown at src/PhpSpreadsheet/Reader/Csv.php:291

    /**
     * Loads Spreadsheet from string.
     */
    public function loadSpreadsheetFromString(string $contents): Spreadsheet
    {
        $spreadsheet = $this->newSpreadsheet();
        $spreadsheet->setValueBinder($this->valueBinder);

        // Load into this instance
        return $this->loadStringOrFile('data://text/plain,' . urlencode($contents), $spreadsheet, true);
    }

    private function openFileOrMemory(string $filename): void
    {
        // Open file
        $fhandle = $this->canRead($filename);
        if (!$fhandle) {
            throw new ReaderException($filename . ' is an Invalid Spreadsheet file.');
        }
        if ($this->inputEncoding === 'UTF-8') {
            $encoding = self::guessEncodingBom($filename);
            if ($encoding !== '') {
                $this->inputEncoding = $encoding;
            }
        }
        if ($this->inputEncoding === self::GUESS_ENCODING) {
            $this->inputEncoding = self::guessEncoding($filename, $this->fallbackEncoding);
        }
        $this->openFile($filename);
        if ($this->inputEncoding !== 'UTF-8') {
            $this->convertNonUtf8($filename);
        }
    }

    protected function convertNonUtf8(string $filename): void
    {

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