Why did the caption generated by this script change to 'Default'?

​@dublove Did you want more information about this? I had a look at the code and it was missing a few guards—I’ve added a few. There are two issues:

(1) Your test document has 30 empty graphics that makes the original script very slow.

(2) As Rob said, the metadata is “default”. I don’t know if some software puts “default” but I’ve put a guard in to ignore it so at least you get the file name.

This script works on the selection but you can give it any array of items.

– Mark

/**
 * @version 2026-08-22
 * @discussion https://community.adobe.com/t5/indesign-discussions/is-there-a-way-to-apply-generic-static-caption-to-all-graphic-containers/m-p/13367937
 * @discussion https://community.adobe.com/questions-671/why-did-the-caption-generated-by-this-script-change-to-default-1635036
 */
function main() {

    if (
        0 === app.documents.length
        || 0 === app.activeDocument.selection.length
    )
        return alert('Please select a graphic frame and try again.');

    var doc = app.activeDocument;
    var items = doc.selection;

    // add caption to each graphic in document
    for (var i = items.length - 1; i >= 0; i--) {
        var item = items[i];

        if (
            !item.hasOwnProperty('graphics')
            || 0 === item.graphics.length
        )
            continue;

        var graphic = item.graphics[0];

        // try to get the graphic's xmp "description"
        var contents = getXMPProperty(graphic, 'description');

        if (
            (!contents || 'default' === contents)
            && graphic.itemLink
        )
            // or fall back to the link filename
            contents = graphic.itemLink.name;

        addCaptionToGraphic(
            {
                doc: doc,
                graphic: graphic,
                contents: contents,
                objectStyleName: 'Caption',
                captionBoxHeight: 40, // pts
                groupCaptionWithGraphic: true,
            }
        );
    }

    /**
     * Adds a caption text frame
     * to the graphic.
     * @author m1b
     * @version 2022-11-24
     * Note: will use "No contents" if contents is empty.
     * @param {Object} options
     * @param {Graphic} options.graphic - an Indesign Graphic.
     * @param {String} options.contents - the text of the caption.
     * @param {String} [options.objectStyleName] - name of the object style to apply.
     * @param {Number|String} [options.captionBoxHeight] - height of the caption box (default: to fit).
     * @param {Boolean} [options.groupCaptionWithGraphic] - whether to group the caption with the graphic's frame.
     * @returns {TextFrame|Group} - the caption's text frame or, if grouped, the group.
     */
    function addCaptionToGraphic(options) {

        app.scriptPreferences.measurementUnit = MeasurementUnits.POINTS;
        options = options || {};

        var doc = options.doc || app.activeDocument;
        var graphic = options.graphic;
        var contents = options.contents || 'No contents';
        var objectStyle = getByName(doc.allObjectStyles, options.objectStyleName);
        var captionBoxHeight = options.captionBoxHeight || 10;
        var captionBox;
        var frame = graphic.parent;
        var b = frame.geometricBounds;

        if (graphic.parentPage == null)
            // don't process graphics on pasteboard
            return;
        // add a frame for the caption text
        captionBox = graphic.parentPage.textFrames.add();
        // set position and size of the caption
        captionBox.geometricBounds = [b[2], b[1], b[2] + captionBoxHeight, b[3]];
        //add caption text
        captionBox.contents = String(contents);
        // expand to handle overflow
        var counter = 0;
        while (
            captionBox.overflows == true
            && counter++ < 1000
        )
            // add 5 pts height
            captionBox.resize(CoordinateSpaces.PARENT_COORDINATES, AnchorPoint.TOP_LEFT_ANCHOR, ResizeMethods.ADDING_CURRENT_DIMENSIONS_TO, [0, 5])
        if (
            objectStyle != undefined
            && objectStyle.isValid
        )
            // set captionBox's object style
            captionBox.applyObjectStyle(objectStyle);
        if (options.groupCaptionWithGraphic !== false)
            // group
            try {
                doc.groups.add([frame, captionBox]);
            } catch (error) { }
    };

    /**
     * Returns a graphic's XMP property contents.
     * Example XMP property names:
     *   author, copyrightInfoURL, copyrightNotice,
     *   copyrightStatus, creationDate, creator,
     *   description, documentTitle, format, jobName,
     *   keywords, modificationDate, serverURL
     * @author m1b
     * @version 2022-11-24
     * @param {Graphic} graphic - an Indesign Graphic.
     * @param {String} property - the desired XMP property name.
     * @returns {String}
     */
    function getXMPProperty(graphic, property) {
        if (!graphic.isValid)
            return;
        try {
            return graphic.itemLink.linkXmp[property];
        } catch (error) {
            /* metadata not available */
        }
    };

    /**
     * Returns a style matching name.
     * @param {Array<style>} styles - an array or collection of styles.
     * @param {String} name - the name to match.
     * @returns {style}
     */
    function getByName(styles, name) {
        for (var i = 0; i < styles.length; i++)
            if (styles[i].name == name)
                return styles[i];
    };

}; // end main

app.doScript(main, ScriptLanguage.JAVASCRIPT, undefined, UndoModes.ENTIRE_SCRIPT, 'Create Captions');