BookStackApp/BookStack · error · Error

Not an image file

Error message

Not an image file

What it means

Guard in the legacy TinyMCE editor's uploadImageFile rejecting a File that is null or has a non-image MIME type, so paste/drop handling only uploads actual images. Input at fault: the pasted or dropped file whose type does not start with 'image'.

Source

Thrown at resources/js/wysiwyg-tinymce/drop-paste-handling.js:17

import {Clipboard} from '../services/clipboard.ts';

let wrap;
let draggedContentEditable;

function hasTextContent(node) {
    return node && !!(node.textContent || node.innerText);
}

/**
 * Upload an image file to the server
 * @param {File} file
 * @param {int} pageId
 */
async function uploadImageFile(file, pageId) {
    if (file === null || file.type.indexOf('image') !== 0) {
        throw new Error('Not an image file');
    }

    const remoteFilename = file.name || `image-${Date.now()}.png`;
    const formData = new FormData();
    formData.append('file', file, remoteFilename);
    formData.append('uploaded_to', pageId);

    const resp = await window.$http.post(window.baseUrl('/images/gallery'), formData);
    return resp.data;
}

/**
 * Handle pasting images from clipboard.
 * @param {Editor} editor
 * @param {WysiwygConfigOptions} options
 * @param {ClipboardEvent|DragEvent} event
 */
function paste(editor, options, event) {

View on GitHub (pinned to 18f8469a1c)

Solutions

1. Check file.type starts with 'image' before calling uploadImageFile
2. Notify the user that only image files can be pasted/dropped as images
3. Handle empty browser file.type with an extension-based fallback check

When it happens

Trigger: Thrown at resources/js/wysiwyg-tinymce/drop-paste-handling.js:17 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BookStackApp/BookStack@18f8469a1c (2026-09-02). Data as JSON: /api/errors/3d51e4c0c45bb971. Report an issue: GitHub.