Embedded vs hosted images in email signatures

Many people face difficulties when it comes to adding images to email signatures. Even after mastering basic tasks, more complex challenges like choosing between embedded and hosted images in email signatures can be confusing.

There’s often a lack of understanding about embedded and hosted images. But it’s not as complex as it sounds.

To put it simply, embedded images are those stored within an email. Hosted images are downloaded and stored on a web server. This reduces the size of the email, making it more mobile-friendly. 

For IT admins managing email signatures centrally across an organization, this decision directly affects how much control you retain over branding after emails are sent and how much overhead you carry when images need updating.

If you’re using Microsoft 365 or Google Workspace, our email signature solution takes the guesswork out. It gives you centralized control over how images are managed and displayed across your entire organization's email signatures.

Should I embed or host images in my email signature?

To include HTML images in email signatures like a company logo or social media icons, you’ve got two image options. You can either embed an image directly into the email signature template or host it externally and link to it. 

Deciding between the two comes down to four factors:

• Email client compatibility: Not all clients render both methods

• Post-send brand control: Hosted images can be updated after the email is sent; embedded images can't

• Email deliverability: Larger payloads can affect delivery and spam filtering

• Operational overhead: Centrally managed hosted images scale better across large organizations

Use the comparison below to see how the two methods stack up, then review the detailed breakdown.

Embedding images

This is when the image is encoded directly into the email as a base64 string or attached to the message.

Pros:

• Displays offline: Once downloaded, images remain visible even if the recipient is offline.

• No external calls: Better for privacy-conscious environments or secure email setups.

• Ideal for internal-only email chains: Works well in controlled environments like Microsoft Outlook or within the same organization.

Cons:

• Increases email size: Emails become heavier, which may slow down load times or trigger spam filters.

• Inconsistent rendering: Some email clients (like Gmail and Apple Mail) strip embedded images, leaving only an attachment.

• Difficult to update: Once sent, the image is locked. If branding or banners need to change, you can’t update them retroactively.

Hosting images (web-linked images)

This is where the image is stored on a server and referenced via a URL in the email signature.

Pros:

• Lightweight emails: Keeps the message size minimal, speeding up delivery and avoiding spam flags.

• Brand control: You can update or change hosted images at any time without needing users to change their signature.

• Tracking capabilities: Allows analytics like image loads and click tracking if hosted via signature management platforms like Exclaimer.

Cons:

• Blocked by default: Some email clients block external images by default, requiring recipients to manually enable them.

• Requires connectivity: Images won’t load if the recipient is offline or behind strict firewalls.

• Potential branding issues: If the image host is down or blacklisted, your branding disappears or appears broken.

When to use each method

Use embedded images when:

• Your recipients primarily use Outlook desktop (2016 or later) or Gmail

• Offline viewing is required for your recipients

• You operate in privacy-conscious or secure email environments

• Your organization doesn't need to update images after emails are sent

• You're sending internal-only communications within a controlled environment

Use hosted images when:

• Recipients primarily view emails on mobile devices

• Your recipients use Microsoft 365, Outlook Web App, or Exchange

• You need to update branding or promotional banners after emails are sent

• Your organization manages email signatures at scale

• You require analytics and tracking capabilities for signature images

• Post-send brand control is a priority

Which email clients support embedded images in email signatures?

Compatibility information last verified: June 2026

Do hosted images in email signatures get blocked by email clients?

Compatibility information last verified: June 2026

* To add a linked image, you need to open the image in a browser and copy it into the Microsoft 365 (Office 365) OWA signature editor. 

** You can add a hosted image by adding the HTML source via the signature editor. 

How to embed images in email signatures 

If you want an image to appear without the recipient having to click a ‘Download Images’ button, we recommend embedding it within the email signature.

Here's how to do it:

Step 1: Add the image to your email signature

Most email clients allow you to add an image to your signature. Insert the image as you normally would, making sure it’s properly sized.

Step 2: Set up the Content-ID reference

When embedding, the image is attached to the email and referenced with a Content-ID. This is done by adding HTML code in the signature's source.

A standard Content-ID will look like this: 

<img src="cid:myimagecid" /> 

Step 3: Save and test

Once you’ve added the Content-ID reference, save your signature and send a test email to yourself. If set up correctly, the image should display automatically without needing to download it. This is because they’re referenced in the source of the message. 

Important considerations

• Embedded images may increase email size, which can cause them to appear as attachments in some clients.

• There are also known issues with images being stripped out of emails and increasing in size on iOS devices. 

How to host images in email signatures 

To prevent images in your email signature from appearing as attachments, you can host them on a web server or a free image hosting site like Imgur or Flickr. This method references the image using a web URL, so the image remains separate from the email itself.

Here’s how to do it:

Step 1: Upload your image

Upload your image to a web server or an image hosting platform. Once uploaded, the platform will provide you with a direct URL to the image file.

Step 2: Link the image in your email signature

Use HTML to reference the hosted image URL in your email signature. A typical example might look like this:

<img src="https://cdn.exclaimer.com/Static2/exclaimer-logo_178x36.png" />

This code links the image to your email signature without attaching it, keeping your email file size smaller.

Step 3: Add alt text (optional but recommended)

Adding alt text (alternative text) ensures that recipients can understand the purpose of the image even if it doesn’t load. You can add alt text by including an alt attribute, like this:

<img src="https://cdn.exclaimer.com/Static2/exclaimer-logo_178x36.png" alt="Exclaimer logo"/>

Important considerations

• Download prompt: Hosted images may prompt recipients to click ‘Download Images’ to view them, a security feature designed to protect against potential risks.

By hosting images this way, you ensure that they aren’t embedded in the email, keeping the email lighter and often improving compatibility across devices and email clients.

Common issues and solutions

Should I use embedded or hosted images in my email signature?

You need to consider how your customers/clients view the emails you send them. The right choice depends on how your recipients and your own users receive email.

• Use embedded images if the majority of your recipients use Outlook desktop (2016 or later) or Gmail, and your organization doesn't need to update images after they're sent.

• Use hosted images if recipients are primarily on Microsoft 365, Outlook Web App, or mobile devices, or if your team needs to update branding centrally after emails go out.

For organizations managing email signatures at scale, hosted images are the lower-maintenance option. When managed centrally through a platform like Exclaimer, image hosting, updates, and tracking are all handled automatically with no manual work required each time branding changes.

Start a free trial and see how easy it is to automate and scale email signatures across teams and devices.