Rendering accuracy
How accurately does MailViewr
simulate each email client?
Not all previews are equal. Most tools render your email in a clean browser environment — but your subscribers open emails in Gmail and Outlook, each of which applies its own color transformation in dark mode.
We built a stress test template covering the most demanding real-world CSS: dark backgrounds, colored CTAs, gradient-adjacent fills, light text on dark panels, and near-white surfaces. We opened it on real physical devices — no emulators — screen-recorded the result, and compared every color swatch pixel-by-pixel against MailViewr's preview. Then we reverse-engineered the algorithm behind each mismatch.
Every accuracy figure on this page has a video to back it up.
| Email client | Platform | Light mode | Dark mode | Status |
|---|---|---|---|---|
Gmail Desktop | Chrome · Safari · Firefox | 100% | N/A | Verified |
Gmail Android | Mobile app | 97% | ~90% | Verified |
Gmail iOS | Mobile app | 95% | 75–80% | Verified |
Outlook Desktop | Chrome · Safari · Firefox | 100% | N/A | Verified |
Outlook Android | Mobile app | 98% | ~70% | Verified |
Outlook iOS | Mobile app | 97% | 70–75% | Verified |
Gmail
Gmail Desktop applies no color transformation — what you write is what renders. Our preview matches this exactly, validated against real browser recordings.
Gmail Android uses CIELAB L* inversion with a brightness threshold. We implement this algorithm directly. Minor deviations on edge-case hues.
Gmail iOS applies unconditional CIELAB L* inversion. Dark navy backgrounds are the primary miss — Gmail iOS shifts them to light blue/lavender. Active improvement in progress.
Outlook
Outlook Desktop rendering is stable and well-documented. Fully verified.
Outlook Android uses undocumented partial color overrides. Dark mode accuracy is still being refined. Light mode is fully verified.
Outlook iOS color override logic is undocumented. This is the most complex client to simulate. Structural accuracy is high; color accuracy is actively being improved.
How we measure accuracy
Stress test template — We designed a standardised HTML email with colour swatches covering the full spectrum: dark navy, blue, green, red, and near-white.
Real device recording — The template is opened on actual devices and screen-recorded. No emulators.
Side-by-side comparison — Each recorded frame is compared against MailViewr's preview pixel-by-pixel for each colour swatch.
Algorithm refinement — Mismatches inform improvements to the inversion pipeline. Accuracy figures are updated after each release.
Outlook mobile dark mode uses undocumented colour override logic. Desktop and light mode accuracy is verified against real device recordings. Beta figures are estimates based on partial validation.