Need to combine two product photos side by side? Stack multiple screenshots into one image? Create a before-and-after comparison? Merging images is one of those tasks that sounds simple but quickly becomes frustrating when you’re jumping between complex tools like Photoshop or uploading files to sketchy websites.
FilesOk’s Image Merger does exactly what you need — combine multiple images vertically or horizontally — in seconds, with zero uploads and zero accounts. Everything runs in your browser.
What Is Image Merging?
Image merging means combining two or more separate images into a single image file. You might need this for:
- Before/After comparisons — Show a product before and after editing
- Social media collages — Combine 2-4 photos into one post
- Product showcases — Display multiple product angles in one image
- Screenshot documentation — Stack multiple screenshots into a single document
- Portfolio layouts — Arrange work samples side by side
Why Use FilesOk to Merge Images?
Most image merging tools either require you to create an account, upload your images to their servers, or install desktop software. FilesOk works differently.
Your files never leave your device. When you use FilesOk’s merger, your images are loaded into your browser’s memory, processed using your device’s own CPU, and downloaded back to your device. At no point does any image travel over the internet or land on a server.
This matters because:
- Privacy: Personal photos, client work, or confidential documents stay private
- Speed: No upload wait times — processing is instant
- Reliability: Works offline after the page loads, no server queues
Step-by-Step: How to Merge Images with FilesOk
Step 1: Open the Merge Tool
Go to filesok.com/okimg/merge-images
You’ll see the file upload zone in the center of the page.
Step 2: Select Your Images
Click “Browse Files” or drag and drop your images directly onto the upload zone.
Important: You need to select at least two images for merging to work. You can select multiple files at once by holding Cmd (Mac) or Ctrl (Windows) while clicking files in your file picker.
FilesOk accepts all common image formats: JPG, PNG, WebP, and GIF.
Step 3: Choose Your Merge Direction
After selecting your files, you’ll see two direction options:
Horizontal — Images are placed side by side, left to right
Best for: Before/after comparisons, product angle shots, landscape collages
Vertical — Images are stacked on top of each other
Best for: Mobile screenshots, step-by-step guides, tall social media posts
Click the button for your preferred direction. You can switch between them at any time before processing.
Step 4: Set the Gap
Below the direction buttons, you’ll find a gap slider ranging from 0px to 50px.
- 0px gap: Images are merged flush — looks seamless
- 10-20px gap: Adds clean white space — good for collages
- 50px gap: Maximum spacing — useful for step-by-step layouts
Drag the slider left or right to set your preferred spacing.
Step 5: Preview
Before processing, click the “Preview” button to see how your merged image will look. This is useful for catching issues — like images being in the wrong order or the direction needing to be switched — before you download.
Step 6: Merge and Download
Click the main action button — it will say “Merge 2 Images” (the number updates based on how many files you selected).
FilesOk processes your images immediately. In most cases this takes under 2 seconds. Once done, click Download File and your merged image saves to your device.
Merge Direction Examples
Horizontal Merge (Side by Side)
Perfect for before/after comparisons. Place the “before” image on the left and “after” on the right with 0px gap for a seamless split image. Add 10px gap if you want a visible divider.
Common uses: Product before/after, two design variants, tool comparisons.
Vertical Merge (Stacked)
Ideal for step-by-step tutorials where the sequence reads top to bottom. Stack three screenshots of a process and you have one image that tells a complete story.
Common uses: Mobile app screenshots, recipe steps, tutorial sequences, infographics.
Tips for Best Results
Match Image Dimensions
When merging horizontally, best results come from images with the same height. When merging vertically, match the widths. If your images have different sizes, use FilesOk’s resize tool first to standardize dimensions, then merge.
Compress Large Files First
FilesOk’s merge tool handles images in your browser’s RAM. Very large images (10MB+ each) may slow processing on older devices. Try compressing them first with FilesOk’s image compressor, then merge.
Gap Color is White
The gap between images uses a white background. If your images have dark backgrounds, set the gap to 0px to avoid a visible white divider.
Output is JPEG
FilesOk exports the merged result as JPEG at 90% quality — excellent quality with minimal compression. Process once and download to avoid re-compression artifacts.
Common Use Cases
Social Media Content
Merging two or three product images horizontally into a single post is a popular technique for Instagram and LinkedIn. A single merged image tells a complete visual story in one frame instead of separate attachments.
Before/After Comparisons
Place the before image and after image side by side with 0px gap for a seamless comparison. Works great for product photography, design work, and photo editing results.
Screenshot Documentation
Combining multiple screenshots vertically is the fastest way to document a process. Stack them into one long image instead of attaching 10 separate screenshots to an email or report.
Client Deliverables
Agencies and freelancers frequently need to show multiple design options side by side. Merge your options horizontally, add a 20px gap between them, and present a clean comparison to your client — without touching Photoshop.
Frequently Asked Questions
How many images can I merge at once? FilesOk supports merging multiple images in one operation. Select all the files you need and they’ll all be included.
Can I merge JPG and PNG together? Yes. FilesOk handles mixed formats in a single merge. The output will be JPEG regardless of input formats.
Does merging reduce image quality? The merge exports at 90% JPEG quality — high quality with minimal visible compression. Process once and download.
Is there a file size limit? No hard limit. The practical limit is your device’s available RAM. Most modern devices handle images up to 20-30MB total without issues.
My images are in the wrong order — can I reorder them? Re-select your files in the correct order. When using your file picker, select them in the sequence you want them to appear.
The Privacy Advantage
Unlike Canva, Adobe Express, or most online mergers, FilesOk never touches your files on a server. When you merge images on FilesOk:
- Your browser downloads the processing code
- Your images are read into your browser’s memory
- Processing happens on your CPU
- The merged result stays in your browser until you download it
- No image data is ever transmitted over the internet
For personal photos, client work, or any images you’d rather keep private — this matters.
Ready to Merge Your Images?
FilesOk’s Image Merger is free, instant, and completely private. No account needed, no upload required, no watermarks added.
Try it right now: filesok.com/okimg/merge-images
Select your images, choose horizontal or vertical, set your gap, and download your merged image in under 10 seconds.