Best tools for dark mode email preview: What we tested (and recommend)

Stripo doesn’t have a built-in dark-mode preview — yet (it’s coming this summer). But with more email clients and devices automatically switching to dark mode, it’s crucial to ensure that your emails look great in both light and dark modes. Poor dark-mode rendering can break layouts, distort brand colors, or make content hard to read.

Although we’re working on a feature that will let you preview emails in both dark and light modes during the design stage, we’ve checked out a few external tools you can use in the meantime — and we’d love to share them with you.

Prep stage

We wanted to make sure that our testing was as fair and realistic as possible. So, we prepared carefully: We selected the most relevant tools and extensions, picked real-life email examples that represent different design scenarios, and tested everything in popular email clients.

Yes, we realize these browser extensions weren’t originally designed for email testing — they’re mostly meant to apply dark mode to websites that don’t support it. But we thought: why not see how they handle emails, too? After all, some of your recipients might be using them while browsing. So, we gave it a try.

How we chose the best dark mode extensions and tools

We selected dark mode extensions and tools based on the following key criteria:

1. Support for popular browsers such as Google Chrome, Safari, Microsoft Edge, and Firefox.
2. Ease and speed of installation and configuration.
3. Performance within the Stripo workspace — with a focus on smooth operation and responsiveness.
4. Compatibility with both Stripo's editing and preview modes.
5. Market share — we checked the number of installs for each plugin and looked at which tools people recommend on forums. Based on these factors, we selected the most popular ones.

We tested eight tools in total but would like to highlight only three. Several had critical issues: Some inverted colors in ways no actual email client would, while others even reversed images, turning them into negatives. These are serious problems that make such tools unreliable for dark mode testing.

Emails we checked

We used three different emails to cover a variety of scenarios:

1. Email 1: With light colors
2. Email 2: Designed with dark colors
3. Email 3: With interactive content

Email 1: Check its web version	Email 2: Check its web version	Email 3: Check its web version

Email clients we used for this test

We aimed to test these emails with all major email clients and operating systems. However, some of them — such as Gmail Web, AOL, both iCloud and Apple Mail on macOS and iOS — don’t truly support dark mode for email content. While their interface may be dark, the actual email section is displayed on a white background, where the colors are not inverted. That’s why we focused our tests on the following clients, which do support dark mode rendering:

• Outlook.com
• Gmail app on iOS
• Gmail app on Android
• Multiple tests with Email on Acid

1. ProofJump’s dark mode simulator

ProofJump dark mode simulator is a cloud-based tool developed by the ProofJump team, who are known for their work in email testing and rendering. This particular simulator focuses on helping marketers preview emails in dark mode. It has a simple interface and does not require a sign-up. It also runs directly in your browser and supports all major email HTML formats.

How to use it

• copy and paste your email code into the tool;
• above the code field, be sure to select the “View in Full screen” mode;
• click on the “Turn on dark mode” toggle;
  
  
• if you make any changes to your email after the first test and want to see how they affect the dark-mode design, you’ll need to either edit the code directly within the tool or return to the Stripo editor, update the design, and then copy and paste the new code into the tool once again.

How to get the code of your email in Stripo:

• once you’ve finished your email, click the Export button above the email editing area;
• in the popup window go to the “File” tab;
• click “HTML;”
• make sure all options like “Minimize HTML” and others are on;
• click “Show HTML code;”
  
  
• copy your code.

Impact on Stripo performance

This tool doesn’t impact how Stripo works in any way.

Results for this tool

Each email had a different design — light, dark, and interactive — which can cause unique rendering issues in dark mode. That’s why we’ll describe the results for each email separately.

Email 1: Designed with light colors

• it showed accurate color inversion, and the colors were close to those displayed by actual email clients;
• this tool mimics the visual output of the following email clients:
  • Outlook.com
  • Outlook Office 365 on Windows 10
  • Outlook 2021 on Windows 11
• actual email clients displayed a higher color contrast than ProofJump’s tool.

In ProofJump (Color contrast ratio* : 5.05)	In Outlook web (Color contrast ratio: 5.44)

Email 2: Designed with dark colors

• some colors were not displayed quite accurately in ProofJump’s tool. While the original email was dark and should have been inverted to light colors in dark mode — as seen in the ProofJump result — most actual email clients rendered the email in dark shades instead, which the simulator could not predict;
• this tool mimics the visual output of the following email clients:
  • Gmail on iOS
  • Outlook 2021 on Windows 11
• further, actual email clients displayed a higher color contrast ratio than ProofJump’s tool — which we consider a positive and reliable result.

In ProofJump (Color contrast ratio: 6.88)	In Gmail on Android (Color contrast ratio: 9.86)

Email 3: With interactive content

• for some reason (we’re still investigating this), the text inside interactive elements — like answer options — was rendered as black on a dark background, making it unreadable. Although, in most actual email clients, the text was displayed correctly: Colors were inverted properly, and contrast was preserved;
• this tool matches the visual output of the following email clients:
  • Outlook Office 365 on Windows 10, where the text was unreadable; in contrast, other email clients inverted the colors correctly, keeping the text readable.

In ProofJump (Color contrast ratio: we did not check here)	In Gmail on iOS (Color contrast ratio: 15.88)

Price

This is a free tool. No registration required.

Tool summary

1. ProofJump is a free, browser-based tool that can be used for testing dark-mode rendering among other things. It doesn’t require installation or sign-up — just paste your HTML code and toggle dark mode on.
2. It works well for designs that use light colors, rendering emails almost exactly as actual email clients do. However, it tends to over-process emails that have already been designed using dark colors and sometimes struggles with text inside interactive elements, making them unreadable.

2. Dark Reader

Dark Mode is a browser extension, so there’s no need to install and run a separate software. Just add it to your browser. It’s fully open-source, ad-free, and, according to its developers, doesn’t collect any user data.

Note: It works in both the preview mode and the email editing area.

How to use it

• Install the extension in your browser and turn it on before you start working on your emails;
• make changes to your emails as necessary with the extension enabled and see the updates in real time;
• alternatively, simply use it for previewing your emails;
• when it’s time to fine-tune your design for the light mode, just turn off the extension (Tip: Pin it to your toolbar for quick access). Sometimes, it takes a few seconds to switch between modes. For example, after turning the extension off, dark mode may remain active briefly before the change takes effect.

You can customize this extension’s settings, which includes adjusting the brightness, contrast, and so on. What’s really convenient is that you can set preferences for individual websites to give each site its own version of dark mode. However, our tests showed that the default settings most closely match how emails are rendered in actual email clients.

Impact on Stripo performance

Using this extension as is won’t affect Stripo’s performance or slow your computer down. But if you start adjusting its settings, it may slow things down; in some cases, you might even need to reboot your device.

Tip: Configure the settings once (they’ll apply to all future use) and then leave them alone 🙂.

Results for this tool

Email 1: Designed with light colors

• it provided fairly accurate color inversion, with colors looking similar to the way they do in actual email clients. However, in the second section of the email, while actual email clients displayed the text in blue, this tool showed it in beige in preview mode;
• this tool mimics the visual output of the following email clients:
  • Outlook.com
  • Outlook Office 365 on Windows 10
  • Outlook 2021 on Windows 11
• the email clients displayed slightly lower color contrast than Dark Reader even after the brightness and contrast were reduced in the settings. So, to ensure your emails maintain strong contrast when viewed by your recipients, aim for slightly higher contrast than what Dark Reader shows in preview mode.

In Dark Reader (Color contrast ratio* : 6.31)	In Outlook web (Color contrast ratio: 5.44)

Email 2: Designed with dark colors

• the colors displayed were very similar to those rendered by actual email clients; dark shades remained dark, while light shades stayed light for most emails, making the preview seem accurate;
• however, the color contrast was noticeably higher in the preview mode than in the actual email clients, just like what was observed for Email 1 (light-color-based design). Keep this in mind when fine-tuning your emails;
• this tool mimics the visual output of the following email clients:
  • the dark-mode preview closely matched the output of all major email clients, which typically preserve dark shades. The only exception was Outlook Office 365 on Windows 10 — while the Windows 11 version showed the email exactly as Dark Reader did.

In Dark Reader (Color contrast ratio: 18.13)	In Gmail on iOS (Color contrast ratio: 12.92)

Out of curiosity, we tested another email designed using dark colors; once again, Dark Reader preserved the dark shades accurately. ProofJump, however, inverted the colors to light shades.

Email 3: With interactive content

• This tool mimics the visual output of the following email clients:
  • the dark-mode preview matched all of them — with the exception of Outlook Office 365 on Windows 10.

In Dark Reader (Color contrast ratio* : 16.37)	In Outlook.com (Color contrast ratio: 16.37)

* Here, we checked the color contrast of the answer option fields, since we had previously encountered issues with them.

Price

Dark Reader is free for individual users on Chrome, Firefox, and Edge, with optional donations encouraged to support development. For organizational use, a recommended annual subscription of $9.99 per user is advised. On Safari (macOS and iOS), Dark Reader is a paid app, available for $5.99 on the App Store.

Tool summary

1. It works in both the email editor and the preview mode, showing results that closely match the outputs of actual email clients.
2. Adjusting custom settings might slow your computer down temporarily, but it’s a one-time setup; once done, you won’t need to tweak them again.
3. The color contrast displayed may be slightly higher than that output by actual email clients, so keep this in mind when designing your emails.

3. Night Eye

Night Eye is a browser extension that automatically converts websites into dark mode and supports 12 major browsers. According to its developers, unlike basic color inverters, it analyzes each page’s color scheme and adjusts it for a more natural, readable dark mode experience.

Note: it works in both the preview mode and the email editing area.

How to use it

Just like the previous tool, you’ll need to install this extension in your browser. It works in both the preview mode and the email editing area. All changes are rendered really quickly.

You can tweak the brightness, contrast, saturation, and more of different elements. We tested various settings but found that the default ones most closely matched the output of actual email clients.

Impact on Stripo performance

Using this extension won’t slow down Stripo or your computer. It’s fast and responsive — changes show up the instant you make them.

Results for this tool

Email 1: Designed with light colors

• in the email editing area, most colors appear as they would in actual email clients;
• however, the tool converted beige into a dark color, while the email clients maintained the beige color with low contrast;
• the overall color contrast that the tool displayed was higher across the entire email compared to that for the actual email clients.

In Night Eye (Color contrast ratio: 8.47)	In Outlook Microsoft 365 (Color contrast ratio: 5.01)

We tested another email with light-color schemes and found that while bright colors were converted correctly, some pastel shades appeared brighter than they would be in actual email clients.

Email 2: Designed with dark colors

• The color contrast in actual email clients was slightly higher than that shown by the tool, which is a good thing;
• in both the email editing area and the preview mode, the colors closely matched the way they appeared in actual email clients;
• this tool mimics the visual output of all major email clients, especially those listed below:
  • Gmail on Android
  • Gmail on iOS
  • AOL

In Night Eye (Color contrast ratio: 17.93)	In Gmail on iOS (Color contrast ratio: 18.04)

Email 3: With interactive content

• it displayed colors almost exactly as actual email clients do, with only slight variations, like showing paler or brighter shades of the same colors;
• color contrast appeared to be lower than that output by the email clients. If the contrast looks good in this tool, you’re more than safe; it’ll look even better in the recipient’s inbox;
• this tool mimics the visual output of most email clients, especially Outlook (web and apps, on Windows and macOS).

In Night Eye (Color contrast ratio: 8.37)	In Gmail on Android (Color contrast ratio: 18.73)

* For consistency, we once again checked the color contrast of the answer option fields.

Price

The free version is limited to one browser and up to five websites of your choice. Paid plans, which support three or more browsers, start at $9 per year.

Tool summary

1. Delivers a realistic dark mode preview in both the editing area and the preview mode that closely matches the output of most major email clients.
2. Shows slightly higher contrast than actual email clients for light designs and slightly lower contrast for dark ones, offering a safe margin for testing.
3. Fast, responsive, and doesn’t affect Stripo’s performance even with custom settings applied.

4. Dark Night Mode

Dark Night Mode is a Chrome extension that applies dark mode to all websites without inverting colors or distorting images. 

Note: it works in both the preview mode and the email editing area.

How to use it

Just like the previous two tools, you’ll need to install this extension in your browser, and it works in both the preview mode and the email editing area. After turning it on, you need to give it a few seconds to apply the changes or, if necessary, refresh the page once or twice. You might need to do this for every new page you open, including when switching from the editing area to the preview mode or opening your email in a new tab.

The allows brightness to be adjusted. However, for email previews, we recommend keeping the default settings, as they deliver the most realistic results.

Impact on Stripo performance

The platform might slow down slightly when generating the “Share” link—that is, when opening your email in a new tab from the preview mode.

Email 1: Designed with light colors

• this tool tended to invert colors a lot. For instance, light beige became brown, and red turned into maroon. In general, all the colors it showed were different from the way they looked in actual email clients;
• blue text was converted into blue text with a shade of gray;
• this tool mimics the visual output of most versions of Outlook — both apps and the web version.

In Dark Night Mode (Color contrast ratio: 2.14)	In Outlook 2021 on Windows (Color contrast ratio: 5.01)

Email 2: Designed with dark colors

• This tool helped us spot an issue on the first screen: It included an image with text and a background in a different color. In light mode, this appeared as a single, unified element; but in some email clients with dark mode, this appeared as two separate sections. We found that this was true for half the email clients we tested. So, if we were to use this template for an actual newsletter, we’d definitely fix that;

The way it renders in light mode	In some email clients with dark mode on

• it changed the color of the buttons from blue to a grayish blue, while the blue text remained unchanged;
• in actual email clients, the color contrast was slightly lower than that shown by the tool, which is something to keep in mind when designing your emails;
• this tool mimics the visual output of most versions of Outlook, both. apps and the web version.

In Dark Night Mode (Color contrast ratio: 18.04)	In Gmail on iOS (Color contrast ratio: 10.34)

Email 3: With interactive content

• as was the case with the first tool, this tool did not convert the color of the text from dark to light in the interactive sections, so it actually ended up displaying dark text on a dark background, which made the copy illegible;
• this tool mimics the visual output of Outlook Office 365 on Windows 10, in which the text was unreadable; other email clients inverted the colors correctly, keeping the text readable.

In Dark Night Mode (Сolor contrast ratio: we did not check this for this case)	In Gmail on Android (Color contrast ratio: 18.73)

Price

This tool is free to use, with no limits on the number of browsers it can be added to. Users can support the project through donations or by contributing to its codebase.

Tool summary

1. It can help you catch design issues early, like conflicting background layers or color mismatches.
2. It may render colors quite differently from actual email clients, especially when light backgrounds and interactive content are involved.
3. It’s fast, easy to use, and doesn’t noticeably affect Stripo’s performance — though you may need to refresh the page when switching views.

How to get closer to what your recipients actually see in dark mode

Here’s what works best: we suggest you use extensions for early design feedback, then test your emails in real environments — either by sending test emails to different inboxes or using tools like Email on Acid. It’s the only way to be sure your emails look right everywhere.

How to run an Email on Acid test in Stripo:

1. Open your email template.
2. Click on “Test” in the top toolbar.
3. In the window that opens, go to the “Email Clients” tab and click on the “Run a Test” button.
4. A new window will open, displaying screenshots of your email across multiple email clients, rendered in both light and dark modes.

Wrapping up

Dark mode can either elevate your email design or completely derail it — especially if you rely on precise branding, layered visuals, or interactive content. That’s why previewing emails in both themes before sending is no longer optional — it's essential.

Here’s what our testing showed:

• every tool or extension has its strengths and limitations. While they’re helpful during the design stage, none can fully emulate how emails will be rendered in actual inboxes across devices and clients;
• results for the different tools tested:
  • ProofJump is fast and reliable for testing light-colored designs, but it can over-process dark themes and cause contrast issues in interactive elements, which actually occurs in a certain version of Outlook;
  • Dark Reader delivers previews that closely match the outputs of actual email clients, especially for dark-themed emails; but the contrast it tends to show is higher than what your recipients will actually see;
  • Night Eye offers natural-looking previews, and while it works well in both the editing and the preview mode, it can brighten pastel shades more than actual email clients do;
  • Dark Night Mode is helpful for spotting hidden layout issues, but its rendering of dark mode often differs significantly from how actual email clients do the same, especially in interactive sections;

• interactive content needs extra attention, as some tools fail to invert the colors of text properly;
• color contrast isn’t always accurate. What looks perfectly legible in a plugin might end up appearing too faint (or too bright) in the inbox. Our advice: design with slightly higher contrast than what the tools display;
• always validate your design in real environments. For the final check, tools like Email on Acid let you see exactly how your email will be rendered by actual email clients across both dark and light mode. This is where you can catch the issues that extensions can’t.

The bottom line:

Browser extensions and plugins = speed. They're great for carrying out quick checks during the design stage to catch obvious issues.

Email testing tools = accuracy. These are essential for the final review before sending your newsletter to your recipients.

Appendix: Comparison table

Tool	Compatab with Stripo editing area	Preview mode	Color inversion accuracy	Color contrast accuracy
ProofJump	No (but lets you edit the code directly in the simulator)	Yes	- Good for light emails; - over-processes dark ones; - does not convert text for interactive elements.	Lower than actual email clients — a pass here means you’re safe.
Dark Reader	Yes	Yes	Reliable for all designs, including interactive content.	Higher than real clients — design with higher contrast.
Night Eye	Yes	Yes	Reliable for all designs, including interactive content. But be cautious with pastel colors.	- Lower than actual email clients for emails that use dark colors and interactive content (a pass here means you’re safe); - higher for emails that use dark colors (design with higher contrast).
Dark Night Mode	Yes	Yes	- The colors it shows might not match those of actual email clients; - reliable for emails that use dark colors; - does not convert the colors of text for interactive elements.	- lower than real email clients for emails in dark colors and interactive content (a pass here means you’re safe); -  higher for emails that use dark colors (design with higher contrast).