Image Dimension Checker

Introduction

Platform image specs are written in pixels: Twitter cards 1200×675, favicon masters 512×512, Shopify product images 2048×2048 recommended. A designer says "should be fine" but the file is 987×612. You could open Preview or Photos, hunt the info panel, and still miss whether the asset is landscape or portrait at a glance. A one-step dimension check saves rejected uploads and broken layouts.

Certoflow's Image Dimension Checker reports width, height, and orientation label the moment you select a file. Large centered text shows 1920 × 1080 pixels (landscape)—or portrait/square as appropriate. Like every Certoflow image tool, inspection runs locally with no server upload.

What this tool does

Select any decodable image file. The tool displays:

• Width in pixels
• Height in pixels
• Orientation classification: landscape, portrait, or square

No secondary panels, no EXIF tables—just the dimensions you need before crop, resize, or CMS upload. Ideal when Metadata Viewer feels like more detail than the task requires.

How it works

Certoflow loads the file through the same loadImageFromFile helper used across image tools. After decode, it compares img.width and img.height:

• Width > height → landscape
• Width < height → portrait
• Equal → square

The result string formats as {width} × {height} pixels ({orientation}) in prominent type for quick reading during batch checks.

Processing is entirely client-side. The file never leaves your browser.

Real-world examples

Hero banner validation. Spec requires minimum 1920 px width. Checker reads 1843 × 1029 pixels (landscape)—reject and request re-export before launch day.

Favicon source check. PWA manifest asks for 512×512 square. Upload shows 512 × 512 pixels (square)—proceed to generate smaller icons in build pipeline.

Instagram portrait post. Creator targets 1080×1350 (4:5). Checker shows 1080 × 1080 pixels (square)—crop vertically before scheduling.

Bug report attachment. QA files ticket: "Image blurry on retina." Dimensions reveal 400×300 asset in 800 CSS pixel slot—root cause is upscaling, not CSS typo.

Print DPI back-of-envelope. Need 300 DPI on 8×10 inch print → roughly 2400×3000 px required. Checker confirms phone export is 3024×4032 portrait—sufficient for vertical print after crop.

Common mistakes

Confusing CSS pixels with image pixels. Layout may show image at 400 px wide while file is 1600 px wide—that is good for retina. Checker reports file pixels; compare to design spec intrinsic requirements.

Ignoring orientation label. 1200 × 1800 (portrait) vs 1800 × 1200 (landscape) matters for cards that assume horizontal art. Read the word in parentheses, not just numbers.

Assuming square when nearly square. 1000×999 reports landscape because width > height. Tiny differences classify orientation; use aspect ratio from Metadata Viewer when near-square decisions matter.

Checking only one dimension. Both width and height must satisfy platform caps—Instagram max dimension limits apply to longest edge depending on platform rules.

Using checker instead of crop when subject framing matters. Dimensions tell size, not composition. A 3000×2000 landscape photo may still crop badly for LinkedIn banner aspect ratio.

Double-counting retina. If spec says "800 px wide" meaning CSS, you may need 1600 file pixels—checker does not multiply; you apply retina math mentally.

Use cases

Developers sanity-check assets in CI manual steps before deploy. Social media managers verify exports from Canva match scheduling tool requirements. Students confirm project screenshots meet rubric minimum resolution.

Webmasters audit legacy content libraries during migrations. Print coordinators reject sub-resolution client JPGs early in the workflow.

Chain with Image Resizer when dimensions are wrong but aspect ratio is acceptable, Crop Image when ratio must change, and format converters when size is fine but MIME type is not.

FAQ

Is my image uploaded?

No. Dimensions are read locally after decode.

Does it show megapixels?

It displays width × height with orientation label, not megapixel totals. Multiply width × height yourself if needed.

Which formats are supported?

JPEG, PNG, WebP, GIF, and other browser-decodable images.

How is landscape vs portrait determined?

Compare width and height after decode. Equal dimensions → square.

Does it read EXIF orientation separately?

Classification uses decoded width/height as reported by the browser Image object.

Can I check multiple files in one view?

One file at a time—re-select to update the display.

Why use this instead of Metadata Viewer?

Dimension Checker optimizes for a fast large readout; Metadata Viewer adds file size, MIME type, and aspect ratio decimal.

Does it work offline?

After page load, yes—no network required for checking.

Can I verify retina (@2x) requirements?

Multiply your CSS layout width by the device pixel ratio mentally. A 960 CSS pixel slot at @2x needs roughly 1920 file pixels wide—the checker reports file pixels, not CSS pixels, so apply that multiplier before comparing to design specs.

What if dimensions look wrong for a phone photo?

Some JPEGs store landscape pixel grids with EXIF rotation tags. If width and height seem swapped relative to how the photo displays in your gallery app, open Rotate Image to bake correct orientation, then re-check dimensions on the exported file.