Image Compare Slider
Compare two photos with a drag slider, a cross-fade blend, or a fixed side-by-side split — horizontal or vertical. Differently-sized photos are cropped to fit, never stretched, and the download always matches exactly what you see.
How to Compare Two Photos
Features
Fixing the Classic Comparison Bug: Stretched Photos
The most common flaw in browser-based before/after tools is forcing both photos into a single fixed canvas size — often whatever size the developer happened to test with — regardless of the photos' actual dimensions. A portrait photo compared against a landscape one, or simply two photos of slightly different resolutions, gets visibly squashed or stretched to fit, which is especially damaging for a tool whose entire purpose is showing an accurate visual difference. This tool crops instead of stretching — the same technique behind CSS's "cover" background sizing — so each photo fills the comparison frame at its correct proportions, with any excess trimmed from the edges rather than the whole image being squeezed. It matters more than it might seem: most real before/after pairs, like an original photo against a resized or re-cropped edit, rarely share identical pixel dimensions in the first place. The exported file follows the same rule as the live preview, at your Before photo's exact resolution — there is no separate, lower-fidelity "screenshot" step that re-introduces the distortion after the fact, which was the specific failure in the version of this tool that existed before this rebuild.
Three Modes, and When to Use Each
Slider is the familiar reveal — a hard divider you drag across the frame — and works best for a change confined to one area of the photo, like a retouched blemish or a repaired section of a wall, where sliding the divider directly across that spot makes the difference unmistakable. Fade cross-dissolves smoothly between the two photos instead of using a hard edge, which is often better for spotting a subtle, photo-wide shift — a color grade, a slight exposure change, a compression quality difference — that a divider line can actually obscure by drawing attention to the edge itself rather than the change. Side-by-Side drops the reveal gesture entirely and shows both photos at once, which suits judging overall composition or layout rather than a pixel-level difference, since nothing is hidden behind a moving line.
Who Reaches for a Compare Slider, and Why
Photographers and retouchers use it constantly — it's the standard way to present editing work, because a reader who drags the divider themselves is actively convinced in a way that scrolling past two flat images never quite achieves. Real estate and interior design accounts use it for renovation before/afters, where the visual impact sells the work far better than a description. Developers and product teams use it to review a UI change with non-technical stakeholders who can't read a diff but can absolutely drag a slider. Researchers and quality-control teams use the more clinical Fade mode to spot subtle differences a hard divider can hide — a slight color cast, a small exposure shift, a compression artifact — since fading between two images makes a faint, photo-wide difference flicker into visibility in a way a static side-by-side view rarely does.
Real-World Use Cases
Photo retouching portfolios: load the unedited original as Before and the retouched version as After — clients who've never seen retouching work understand it immediately when they drag the reveal themselves, which is far more persuasive than two static images side by side in a deck. Evaluating compression quality: compress a photo at two quality levels with the Image Compressor, then compare the original against the compressed version — JPEG artifacts in high-frequency detail like hair or foliage become obvious as the divider crosses them, more reliable than judging a quality percentage number alone. Web design reviews: screenshot an old interface and a new one, and let stakeholders who don't read code explore the change directly. Timelapse-style comparisons: the same scene photographed months apart — a construction site, a garden, a renovation — with custom labels like dates instead of "Before"/"After". None of these require the two photos to be technically related in any way beyond sharing the same frame — the tool simply overlays whatever two images it's given and lets the chosen mode reveal one against the other, so a landscape photographed in different seasons works just as well as a deliberate retouching comparison.
Choosing an Orientation
Horizontal is the default for a reason — most photos and most changes read left-to-right — but it isn't always the right axis. A change running mostly vertically, like a repainted wall, a replaced door, or anything else where the boundary of the change is roughly vertical itself, is easier to judge with a Vertical wipe or split, since the divider then crosses the change perpendicular to it rather than parallel, making the boundary between old and new far more obvious at a glance. The same logic applies to Side-by-Side: a pair of tall portrait photos usually reads better stacked vertically than squeezed side by side into two narrow columns.
Getting a Comparison That Actually Convinces
The two photos need to be aligned the same way for the comparison to read cleanly — the same framing, the same distance from the subject, ideally shot from a tripod or the same handheld position, since even a small shift makes the divider reveal a camera-angle change instead of the actual edit. Positioning the divider at the exact boundary of the change, rather than leaving it parked at 50%, is what actually demonstrates the difference — a viewer left to find it themselves often misses a localized edit entirely. For a subtle, whole-photo change like a color grade, Fade mode at a slow manual scrub through 0–100% reveals more than a Slider ever will, since the eye is very good at detecting a photo-wide shift during a cross-fade but comparatively bad at noticing it across a hard-edged divider.
What This Tool Won't Do
It compares two photos you already have — it doesn't generate the "after" version for you. To create a genuinely edited version to compare against the original, apply an effect first with Image Filters or convert to black-and-white with Grayscale, then load both the original and the edited result here. And if the goal is resizing one photo to exactly match the other's dimensions rather than letting this tool crop for the comparison, the Image Resizer handles that directly.