Save for Web needs a file size limiter tool that adjusts the dimensions of a GIF.

[Josh32367144i052]

For social media posts there are file size limits on GIFs. For instance, Facebook is 5MB. I typically will hit this target in the Save for Web panel by adjusting the dimensions of the GIF until the file size is under 5MB. This is a tedious process that can definitely be sped up. I suggest a tool that allows you to input the file size target. It then automatically adjusts the dimensions of the GIF accordingly.

[Stephen Marsh]

Save for Web (Legacy) already has an option to limit via a target file size, however, I'm not sure if it works with animated GIFs or adjusting the dimensions. This might need to be scripted.

Also, as a (Legacy) feature, I wouldn't hold my breath on seeing any new features being added to this old code.

[Stephen Marsh · Accepted solution]

Looks like the Optimise to File Size... feature does work for animated GIF files, however, it has a max limit of 2048K and it doesn't resize the px dimensions:

A custom script would be required to reduce dimensions to achieve a target size on drive, while retaining your other GIF options such as number of colours, dither etc.

EDIT: I have created a "proof of concept" script, it still needs further testing.

[Stephen Marsh]

Here is the script that I mentioned. Select a target file size between 1-5 MB in half increments and canvas resize in 5% or 10% increments:

/* 
Export GIF to Target File Size.jsx
Stephen Marsh
v1.0 - 14th June 2025
Info: Save the active document as GIF, scaling the canvas size down in 10% increments until the file size on drive is under specified limit
https://community.adobe.com/t5/photoshop-ecosystem-discussions/save-for-web-needs-a-file-size-limiter-tool-that-adjusts-the-dimensions-of-a-gif/td-p/15369326
*/

// Global variables
var theDirPath = "~/Desktop"; // Default directory path
var theDocName = app.activeDocument.name.replace(/\.[^\.]+$/, '');
var theFilePath;
var theScale = 100;
var minScale = 20; // Don't go below 20% scale
var scaleIncrement = 10; // Default scale reduction increment
var maxSize = 5 * 1024 * 1024; // Default 5MB in bytes
var colTableLength = 256; // Default color table length
var colorReductionAlgorithm = stringIDToTypeID("adaptive"); // Adaptive - stringIDToTypeID("adaptive") || Perceptual - charIDToTypeID( "Prcp" )


// Create UI
function createUI() {
    var dialog = new Window("dialog", "Export GIF to Target File Size (v1.0)");
    dialog.orientation = "column";
    dialog.alignChildren = "fill";
    dialog.spacing = 10;
    dialog.margins = 16;

    // Main panel
    var mainPanel = dialog.add("panel", undefined, "Export Settings");
    mainPanel.orientation = "column";
    mainPanel.alignChildren = "fill";
    mainPanel.spacing = 10;
    mainPanel.margins = 16;

    // Directory selection group
    var dirGroup = mainPanel.add("group");
    dirGroup.orientation = "row";
    dirGroup.alignChildren = "center";
    dirGroup.spacing = 10;

    dirGroup.add("statictext", undefined, "Output Directory:");
    var dirDisplay = dirGroup.add("edittext", undefined, theDirPath);
    dirDisplay.preferredSize.width = 300;
    dirDisplay.enabled = false;

    var browseButton = dirGroup.add("button", undefined, "Browse...");
    browseButton.preferredSize.width = 80;

    // File size dropdown group
    var sizeGroup = mainPanel.add("group");
    sizeGroup.orientation = "row";
    sizeGroup.alignChildren = "center";
    sizeGroup.spacing = 10;

    sizeGroup.add("statictext", undefined, "Maximum File Size (MB):");
    var sizeArray = [1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5];
    var sizeDropdown = sizeGroup.add("dropdownlist", undefined, sizeArray);
    sizeDropdown.selection = 8; // Default to 5MB (index 8)
    sizeDropdown.preferredSize.width = 80;

    // Scale increment dropdown group
    var scaleGroup = mainPanel.add("group");
    scaleGroup.orientation = "row";
    scaleGroup.alignChildren = "center";
    scaleGroup.spacing = 10;

    scaleGroup.add("statictext", undefined, "Canvas Scale Reduction:");
    var scaleArray = ["5%", "10%"];
    var scaleDropdown = scaleGroup.add("dropdownlist", undefined, scaleArray);
    scaleDropdown.selection = 1; // Default to 10% (index 1)
    scaleDropdown.preferredSize.width = 80;

    // Button group
    var buttonGroup = dialog.add("group");
    buttonGroup.orientation = "row";
    buttonGroup.alignment = "right";
    buttonGroup.spacing = 10;

    var cancelButton = buttonGroup.add("button", undefined, "Cancel");
    var okButton = buttonGroup.add("button", undefined, "OK");

    // Event handlers
    browseButton.onClick = function () {
        var folder = Folder.selectDialog("Select Output Directory", theDirPath);
        if (folder) {
            theDirPath = folder.fsName;
            dirDisplay.text = theDirPath;
        }
    };

    cancelButton.onClick = function () {
        dialog.close(0);
    };

    okButton.onClick = function () {
        if (sizeDropdown.selection && scaleDropdown.selection) {
            maxSize = sizeDropdown.selection.text * 1024 * 1024; // Convert MB to bytes
            scaleIncrement = parseInt(scaleDropdown.selection.text); // Extract number from "5%" or "10%"
            dialog.close(1);
        } else {
            alert("Please select both maximum file size and scale reduction step.");
        }
    };

    return dialog;
}

(function () {
    try {
        // Check if there's an active document
        if (!app.documents.length) {
            alert("No active document found. Please open a document first.");
            return;
        }

        // Show UI dialog
        var dialog = createUI();
        var result = dialog.show();

        // Exit if user cancelled
        if (result === 0) {
            return;
        }

        // Set the file path
        theFilePath = theDirPath + "/" + theDocName + ".gif";
        var fileObj = new File(theFilePath);

        // Calculate maximum attempts
        var maxAttempts = Math.floor((100 - minScale) / scaleIncrement) + 1;
        var currentAttempt = 1;

        // Create progress window
        var progressWindow = createProgressWindow();

        try {
            // Loop: Save and check file size, reduce scale if needed
            while (true) {
                // Check if user cancelled
                if (progressWindow.isCancelled()) {
                    return;
                }

                // Update progress
                progressWindow.updateProgress(theScale, null, currentAttempt, maxAttempts);

                saveForWebGIF(theDirPath, theFilePath, theScale, theScale);

                // Wait to ensure that the file is written before checking its size
                $.sleep(500);

                fileObj = new File(theFilePath);
                if (fileObj.exists) {
                    fileObj.open("r");
                    var fileSize = fileObj.length;
                    fileObj.close();

                    // Update progress with file size
                    progressWindow.updateProgress(theScale, fileSize, currentAttempt, maxAttempts);

                    if (fileSize <= maxSize) {
                        progressWindow.close();
                        alert("GIF saved under " + (maxSize / 1024 / 1024) + "MB at " + theScale + "% scale. File size: " + (fileSize / 1024).toFixed(2) + " KB");
                        break;
                    } else {
                        theScale -= scaleIncrement;
                        currentAttempt++;
                        if (theScale < minScale) {
                            progressWindow.close();
                            alert("Could not reduce file under " + (maxSize / 1024 / 1024) + "MB even at minimum (" + minScale + "% scale). File size: " + (fileSize / 1024).toFixed(2) + " KB");
                            break;
                        }
                    }
                } else {
                    progressWindow.close();
                    alert("Failed to save GIF file.");
                    break;
                }
            }
        } catch (e) {
            progressWindow.close();
            throw e;
        }
    } catch (e) {
        alert("Error: " + e.message);
    }
})();


///// Functions /////
function saveForWebGIF(outputDirPath, outputDirFilePath, hScale, vScale) {
    var descriptor = new ActionDescriptor();
    var descriptor2 = new ActionDescriptor();
    var descriptor3 = new ActionDescriptor();
    var descriptor4 = new ActionDescriptor();
    var descriptor5 = new ActionDescriptor();
    var descriptor6 = new ActionDescriptor();
    var descriptor7 = new ActionDescriptor();
    var descriptor8 = new ActionDescriptor();
    var descriptor9 = new ActionDescriptor();
    var descriptor10 = new ActionDescriptor();
    var descriptor11 = new ActionDescriptor();
    var descriptor12 = new ActionDescriptor();
    var descriptor13 = new ActionDescriptor();
    var descriptor14 = new ActionDescriptor();
    var descriptor15 = new ActionDescriptor();
    var descriptor16 = new ActionDescriptor();
    var descriptor17 = new ActionDescriptor();
    var list = new ActionList();
    var list2 = new ActionList();
    descriptor2.putEnumerated(charIDToTypeID("Op  "), charIDToTypeID("SWOp"), charIDToTypeID("OpSa"));
    descriptor2.putBoolean(charIDToTypeID("DIDr"), true);
    descriptor2.putPath(stringIDToTypeID("in"), new File(outputDirPath));
    descriptor2.putString(stringIDToTypeID("pathName"), outputDirFilePath);
    descriptor2.putEnumerated(stringIDToTypeID("format"), charIDToTypeID("IRFm"), charIDToTypeID("GIFf"));
    descriptor2.putBoolean(stringIDToTypeID("interfaceIconFrameDimmed"), false);
    descriptor2.putEnumerated(charIDToTypeID("RedA"), charIDToTypeID("IRRd"), colorReductionAlgorithm); // Adaptive or Perceptual
    descriptor2.putBoolean(charIDToTypeID("RChT"), false);
    descriptor2.putBoolean(charIDToTypeID("RChV"), false);
    descriptor2.putBoolean(charIDToTypeID("AuRd"), false);
    descriptor2.putInteger(charIDToTypeID("NCol"), colTableLength); // Number of colors in the color table
    descriptor2.putInteger(charIDToTypeID("DChS"), 0);
    descriptor2.putInteger(charIDToTypeID("DCUI"), 0);
    descriptor2.putBoolean(charIDToTypeID("DChT"), false);
    descriptor2.putBoolean(charIDToTypeID("DChV"), false);
    descriptor2.putInteger(charIDToTypeID("WebS"), 0);
    descriptor2.putEnumerated(charIDToTypeID("TDth"), charIDToTypeID("IRDt"), stringIDToTypeID("none"));
    descriptor2.putInteger(charIDToTypeID("TDtA"), 100);
    descriptor2.putInteger(charIDToTypeID("Loss"), 0);
    descriptor2.putInteger(charIDToTypeID("LChS"), 0);
    descriptor2.putInteger(charIDToTypeID("LCUI"), 100);
    descriptor2.putBoolean(charIDToTypeID("LChT"), false);
    descriptor2.putBoolean(charIDToTypeID("LChV"), false);
    descriptor2.putBoolean(stringIDToTypeID("transparency"), true);
    descriptor2.putBoolean(charIDToTypeID("Mtt "), true);
    descriptor2.putEnumerated(stringIDToTypeID("dither"), charIDToTypeID("IRDt"), stringIDToTypeID("diffusion"));
    descriptor2.putInteger(stringIDToTypeID("ditherAmount"), 100);
    descriptor2.putInteger(charIDToTypeID("MttR"), 255);
    descriptor2.putInteger(charIDToTypeID("MttG"), 255);
    descriptor2.putInteger(charIDToTypeID("MttB"), 255);
    descriptor2.putUnitDouble(charIDToTypeID("HScl"), stringIDToTypeID("percentUnit"), hScale);
    descriptor2.putUnitDouble(charIDToTypeID("VScl"), stringIDToTypeID("percentUnit"), vScale);
    descriptor2.putBoolean(charIDToTypeID("SHTM"), false);
    descriptor2.putBoolean(charIDToTypeID("SImg"), true);
    descriptor2.putEnumerated(charIDToTypeID("SWsl"), charIDToTypeID("STsl"), charIDToTypeID("SLAl"));
    descriptor2.putEnumerated(charIDToTypeID("SWch"), charIDToTypeID("STch"), charIDToTypeID("CHsR"));
    descriptor2.putEnumerated(charIDToTypeID("SWmd"), charIDToTypeID("STmd"), charIDToTypeID("MDNn")); // "MDNn" for no metadata | "MDAl" for all metadata
    descriptor2.putBoolean(charIDToTypeID("ohXH"), false);
    descriptor2.putBoolean(charIDToTypeID("ohIC"), true);
    descriptor2.putBoolean(charIDToTypeID("ohAA"), true);
    descriptor2.putBoolean(charIDToTypeID("ohQA"), true);
    descriptor2.putBoolean(charIDToTypeID("ohCA"), false);
    descriptor2.putBoolean(charIDToTypeID("ohIZ"), true);
    descriptor2.putEnumerated(charIDToTypeID("ohTC"), charIDToTypeID("SToc"), charIDToTypeID("OC03"));
    descriptor2.putEnumerated(charIDToTypeID("ohAC"), charIDToTypeID("SToc"), charIDToTypeID("OC03"));
    descriptor2.putInteger(charIDToTypeID("ohIn"), -1);
    descriptor2.putEnumerated(charIDToTypeID("ohLE"), charIDToTypeID("STle"), charIDToTypeID("LE03"));
    descriptor2.putEnumerated(charIDToTypeID("ohEn"), charIDToTypeID("STen"), charIDToTypeID("EN00"));
    descriptor2.putBoolean(charIDToTypeID("olCS"), false);
    descriptor2.putEnumerated(charIDToTypeID("olEC"), charIDToTypeID("STst"), charIDToTypeID("ST00"));
    descriptor2.putEnumerated(charIDToTypeID("olWH"), charIDToTypeID("STwh"), charIDToTypeID("WH01"));
    descriptor2.putEnumerated(charIDToTypeID("olSV"), charIDToTypeID("STsp"), charIDToTypeID("SP04"));
    descriptor2.putEnumerated(charIDToTypeID("olSH"), charIDToTypeID("STsp"), charIDToTypeID("SP04"));
    descriptor3.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC00"));
    list.putObject(charIDToTypeID("SCnc"), descriptor3);
    descriptor4.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC19"));
    list.putObject(charIDToTypeID("SCnc"), descriptor4);
    descriptor5.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC28"));
    list.putObject(charIDToTypeID("SCnc"), descriptor5);
    descriptor6.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC24"));
    list.putObject(charIDToTypeID("SCnc"), descriptor6);
    descriptor7.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC24"));
    list.putObject(charIDToTypeID("SCnc"), descriptor7);
    descriptor8.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC24"));
    list.putObject(charIDToTypeID("SCnc"), descriptor8);
    descriptor2.putList(charIDToTypeID("olNC"), list);
    descriptor2.putBoolean(charIDToTypeID("obIA"), true);
    descriptor2.putString(charIDToTypeID("obIP"), "");
    descriptor2.putEnumerated(charIDToTypeID("obCS"), charIDToTypeID("STcs"), charIDToTypeID("CS01"));
    descriptor9.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC01"));
    list2.putObject(charIDToTypeID("SCnc"), descriptor9);
    descriptor10.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC20"));
    list2.putObject(charIDToTypeID("SCnc"), descriptor10);
    descriptor11.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC02"));
    list2.putObject(charIDToTypeID("SCnc"), descriptor11);
    descriptor12.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC19"));
    list2.putObject(charIDToTypeID("SCnc"), descriptor12);
    descriptor13.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC06"));
    list2.putObject(charIDToTypeID("SCnc"), descriptor13);
    descriptor14.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC24"));
    list2.putObject(charIDToTypeID("SCnc"), descriptor14);
    descriptor15.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC24"));
    list2.putObject(charIDToTypeID("SCnc"), descriptor15);
    descriptor16.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC24"));
    list2.putObject(charIDToTypeID("SCnc"), descriptor16);
    descriptor17.putEnumerated(charIDToTypeID("ncTp"), charIDToTypeID("STnc"), charIDToTypeID("NC22"));
    list2.putObject(charIDToTypeID("SCnc"), descriptor17);
    descriptor2.putList(charIDToTypeID("ovNC"), list2);
    descriptor2.putBoolean(charIDToTypeID("ovCM"), false);
    descriptor2.putBoolean(charIDToTypeID("ovCW"), false);
    descriptor2.putBoolean(charIDToTypeID("ovCU"), false);
    descriptor2.putBoolean(charIDToTypeID("ovSF"), true);
    descriptor2.putBoolean(charIDToTypeID("ovCB"), true);
    descriptor2.putString(charIDToTypeID("ovSN"), "images");
    descriptor.putObject(stringIDToTypeID("using"), stringIDToTypeID("SaveForWeb"), descriptor2);
    executeAction(stringIDToTypeID("export"), descriptor, DialogModes.NO);
}

function createProgressWindow() {
    var progressWindow = new Window("window", "Exporting GIF...");
    progressWindow.orientation = "column";
    progressWindow.alignChildren = "fill";
    progressWindow.spacing = 10;
    progressWindow.margins = 16;
    progressWindow.preferredSize.width = 400;

    // Status text
    var statusText = progressWindow.add("statictext", undefined, "Initializing export...");
    statusText.preferredSize.width = 380;

    // Progress bar
    var progressBar = progressWindow.add("progressbar", undefined, 0, 100);
    progressBar.preferredSize.width = 380;
    progressBar.preferredSize.height = 10;

    // Scale and file size info
    var scaleText = progressWindow.add("statictext", undefined, "Scale: 100%");
    var sizeText = progressWindow.add("statictext", undefined, "File size: Calculating...");

    // Cancel button
    var buttonGroup = progressWindow.add("group");
    buttonGroup.alignment = "center";
    var cancelButton = buttonGroup.add("button", undefined, "Cancel");

    var cancelled = false;
    cancelButton.onClick = function () {
        cancelled = true;
        progressWindow.close();
    };

    progressWindow.show();

    return {
        window: progressWindow,
        statusText: statusText,
        progressBar: progressBar,
        scaleText: scaleText,
        sizeText: sizeText,
        isCancelled: function () { return cancelled; },
        updateProgress: function (scale, fileSize, attempt, maxAttempts) {
            if (cancelled) return;

            var progress = ((100 - scale + 10) / (100 - minScale + 10)) * 100;
            this.progressBar.value = Math.min(progress, 100);

            this.statusText.text = "Attempt " + attempt + " of " + maxAttempts + " - Testing scale " + scale + "%";
            this.scaleText.text = "Scale: " + scale + "%";

            if (fileSize) {
                var sizeMB = (fileSize / 1024 / 1024).toFixed(2);
                var targetMB = (maxSize / 1024 / 1024).toFixed(1);
                this.sizeText.text = "File size: " + sizeMB + "MB (Target: <" + targetMB + "MB)";
            }

            this.window.update();
        },
        close: function () {
            this.window.close();
        }
    };
}

[Stephen Marsh]

@Josh32367144i052 

Are you still out there?

[melissapiccone]

I find this very amusing - welcome to my life in 1997 when I had to make animated banner ads that had to be less than 10k. You need to old school it to get those files sizes down - reduce the number of colors, the dithering makes the file size larger, etc. We didnt have fancy tools to help us back then. Sounds like Stephen has some better ideas. 

[Stephen Marsh]

@melissapiccone 

Having gone through things the hard way with banner ads and restricitve specs back in the late 90's, you have a great grounding!

I'm guessing that in this case @Josh32367144i052 is just wanting to upload a long "animated gif silent video" which is why there is a 5mb limit and the pixel dimensions are irrelevant.