The email signature image size that works is a logo between 70 and 100 pixels high and 300 to 400 pixels wide for Gmail, which publishes exactly those numbers. Outlook and Apple Mail publish no pixel figure, so you resize to the same footprint, export it sharp, and keep the file light. Here is each limit with its source, and the Smol setting that meets it.
| What you are adding | The limit you hit | The Smol setting |
|---|---|---|
| A company logo for Gmail | Recommended 70–100 px high by 300–400 px wide; maximum 100 px high by 1000 px wide | Compress, PNG or JPG, maximum dimension 400, quality 75 |
| A logo for Outlook | No pixel or file-size limit published; formats .bmp, .gif, .jpg, .png | Same footprint as Gmail so one file works everywhere |
| A blurry logo | Image exported at its display size, then shown on a high-density screen | Export at 2× the display width in a pixel-size run, then set the size in the mail client |
| A headshot or banner that is too heavy | Gmail counts the image toward its 10,000-character signature limit and errors | Lower the maximum dimension, then lower quality |
| A signature that leaks location or camera data | Photos carry EXIF and GPS fields | Metadata stripping is on by default for images |
What is the Gmail signature image size limit?
Gmail recommends 70–100 pixels high by 300–400 pixels wide and states a maximum of 100 pixels high by 1000 pixels wide. Those are the only pixel figures Google publishes for signature images, in its signature troubleshooting page.
| Mail client | Pixel size | File size and format | Source |
|---|---|---|---|
| Gmail | Recommended 70–100 high × 300–400 wide; maximum 100 high × 1000 wide | No file-size cap stated. The image counts toward the 10,000-character signature limit | Troubleshoot, Create a signature |
| Outlook for Windows (classic) | No pixel limit stated; resize by dragging, or right-click the image, Picture, Size, with Lock aspect ratio on | Files should use a .bmp, .gif, .jpg or .png extension. No file-size cap stated | Photo and links, Brand your business |
| Outlook for Mac | No pixel limit stated | Signatures can contain text, links and pictures. No file-size cap stated | Outlook for Mac |
| Apple Mail on Mac | No pixel limit stated | Add an image by dragging it into the preview area. No file-size cap stated | Mail User Guide |
Neither Google nor Microsoft publishes a gmail signature image size in kilobytes, so none is in the table. After uploading, Gmail lets you pick Small, Medium, Large or Original size, which changes how the image is shown, not how many pixels the file holds.
- Gmail takes an image from a public web address, a public file in My Drive, or an upload. A Drive image must have its sharing set to public.
- If you hit an error, Google’s advice is to resize the image. That is the step Smol does in bulk.
Why is my Outlook signature image too large?
Usually because the pasted picture is a full-size file the editor displays shrunken. Microsoft publishes no size cap for Outlook, so the fix is to resize the source file itself, not drag the corner handle.
Dragging resizes how it looks, not the bytes inside. A 3000-pixel-wide logo shown at 300 pixels still carries all 3000 pixels, and that is what makes the signature heavy on every outgoing message. Microsoft’s instructions tell you to resize with the Picture dialog and keep Lock aspect ratio checked, which keeps the shape but not the weight. Its brand-your-business page also warns that Vector Markup Language (VML) tags in a signature can make some elements show up as attachments, so insert the picture with the Image button rather than pasting markup.
The reliable order is: shrink the file to its final pixel size first, then insert it, then leave it at 100%. That also fixes the case where one colleague’s logo looks bigger than another’s: both were scaled by eye.
What signature logo size should I use?
For the right email signature image size, pick the width you want to see, then export at twice that. A logo meant to appear 200 pixels wide is exported 400 pixels wide, so high-density screens have pixels to spare. The factor of two is our rule of thumb, not a vendor figure, and Gmail’s own limits cap how far it can go.
| Image | Display size | Export size | Why |
|---|---|---|---|
| Wide logo, Gmail | 300 × 80 px | 300–400 px wide, up to 100 px high | Stays inside Gmail’s recommended 300–400 × 70–100 |
| Wide logo, Outlook or Apple Mail | 200 × 60 px | 400 × 120 px, shown at 50% | No published limit; 2× keeps edges crisp |
| Square mark | 80 × 80 px | 160 × 160 px shown at 50% (Gmail: 100 × 100 px) | Small icon, small file |
| Headshot | 100 × 100 px | 200 × 200 px shown at 50% (Gmail: 100 × 100 px) | Faces need the extra pixels |
| Social icons | 20–24 px | 40–48 px | Tiny images, but still sharper at 2× |
Why is my email signature image blurry?
Usually the file has too few pixels for the size it is shown at, or the mail client enlarged it. A 100-pixel-wide logo displayed at 100 pixels looks soft on a screen that packs two pixels into each one, and a small file stretched to 300 pixels looks worse.
- Too few pixels. Re-export the logo from the original artwork at 2× the display width. Smol can enlarge a raster image 2×, 3× or 4×, but it only guesses at detail, so treat that as a last resort when the source is lost.
- Over-compressed. JPG on a flat-color logo shows halos around letters. Use PNG for logos and flat graphics, JPG for photos.
- Scaled by the client. In Gmail, choose Original size rather than a size option after uploading; in classic Outlook, resize only with Lock aspect ratio on.
- Wrong aspect. Squashing a logo to fit a column warps it. Keep the proportions and change the width only.
Smol has no SVG support, so a vector logo has to be exported to PNG or JPG first. It also has no lossless mode for images: every pass re-encodes. If a thin-line logo shows banding, raise the quality and compare, because 75 is a default, not a guarantee for line art.
Which Smol settings give the right email signature image size?
Use Compress, set the maximum dimension to the width you want, and keep quality near the default. Smol resizes images to fit inside 2000 × 2000 pixels unless you change it, so a signature logo needs the dimension set lower than that.
| Image | Operation and format | Quality | Maximum dimension |
|---|---|---|---|
| Flat-color logo | Compress, output PNG | 75; raise if edges look soft | 400 |
| Photographic logo or banner | Compress, output JPG | 75 to 80 | 400 |
| Headshot | Compress, output JPG | 80 | 200 (Gmail: 100) |
| Icon set | Compress, output PNG | 75 | 48 |
| An old, oversized signature photo | Compress, same format | 75 | Lower until the file is small enough for your mail client |
Fit mode scales the image to fit inside the box and keeps its shape, so a 400 × 100 banner set to 400 comes out 400 pixels wide. Fill crops with no control over what is cut, so avoid it for logos. Smol writes a copy with the _compressed suffix beside the original and, by default, leaves the original alone. Metadata is stripped by default, which removes EXIF, GPS, IPTC and XMP.
For scale only: on 24 small Kodak test photos at 768 × 512, Smol’s PNG-to-PNG pass at quality 75 saved 69.2%. Those are film photographs, not logos, and a flat logo is often already small, so see the benchmark page for the method and read the output size file by file.
How do I resize and compress a signature image on a Mac?
Drop the file in, set the size, and paste the result.
Start from the biggest, cleanest original
Use the original artwork exported large, not a screenshot of your current signature.
Drag it into Smol
A folder works too, which helps when a team shares one logo set.
Choose Compress, then PNG for logos or JPG for photos
Set quality to 75 and the maximum dimension to your target width from the settings table.
Run it and check the output
Smol shows per-file savings. Open the copy and zoom to 100% to check the edges.
Insert it in your mail client
In Apple Mail, drag the image into the signature preview area. In Gmail, upload it, or point to a public web address. In Outlook, use the Image button.
Send yourself a test
Open it on a laptop and a phone. If it looks soft, go back and export wider; if the client rejects it, go smaller.
What do people use to resize signature images today?
The free tools are good enough for one logo. Smol earns its place when you do this for many people, or want sharper control of pixels and quality.
| Option | What it does well | Where it falls short |
|---|---|---|
| Gmail size options (Small, Medium, Large, Original) | No extra app | Scales display only; cannot add pixels or cut file weight |
| Preview on Mac (Tools, Adjust Size) | Free, exact pixel width | One image at a time; no quality control |
| The sips command | Free, scriptable. See the sips guide | Terminal only; no preview |
| Automator | Free batches. See the Automator guide | Setup time; fragile |
| Free web compressors | Quick for one file | Your logo is uploaded to a server |
| Smol | Pixel size, quality and format in one pass, local, batch | Paid; no SVG; not the fastest tool |
Related reading: the sips command, batch resizing in Automator and every Mac compression method compared.
For an office with many signatures
Solo is $29 once for one Mac. Team is $49 once for three Macs; Enterprise is $20 a seat once, for 5 to 500 seats. Presets are saved per Mac, so to keep signatures consistent, write down the width, format and quality and recreate the preset on each Mac. A four-person office buys Team plus Solo. See pricing. For more on sending files to clients, see small business email attachments and marketing teams.
When is Smol the wrong tool for signature images?
Skip Smol in these cases:
- You need a signature built from a template, with links and layout. Smol resizes images; it does not build signatures.
- You want a company-wide signature applied centrally by an admin. That is a mail-server job, not an image job.
- Your logo is an SVG. Smol has no SVG support; export a PNG from your design tool first.
- You need pixel-identical optimization. Smol always re-encodes; ImageOptim has a lossless mode.
- You are on Windows or Linux. Smol is Mac only.
Frequently asked questions
What is the best email signature image size?
For Gmail, Google recommends 70–100 pixels high by 300–400 pixels wide, with a stated maximum of 100 pixels high by 1000 pixels wide. Outlook and Apple Mail publish no pixel figure for signature images, so use the same footprint, send yourself a test email, and check it on a laptop and a phone before rolling it out to a team.
What is the Gmail signature image size limit?
Gmail states a maximum of 100 pixels high by 1000 pixels wide for signature images and a 10,000-character limit for the whole signature, which the image counts toward. Google gives no file-size cap in kilobytes. If Gmail shows an error, its advice is to resize the image, so lower the pixel dimensions first and then the quality setting.
Why is my Outlook signature image too large?
Usually the picture file has far more pixels than it is shown at, and Outlook merely displays it smaller. Resize the source file to its final pixel width before inserting it. Microsoft publishes no size cap for signature images, so the practical limit is what recipients’ mail servers accept. Keep the file small and the pixel size close to the display size.
How do I fix a blurry email signature image?
Re-export the logo from the original artwork at about twice the display width, use PNG for flat logos, and insert it at 100% rather than stretching it. In Gmail keep within the 100-pixel-high maximum. Check the result on a phone and a laptop, because the same image can look sharp on one and soft on the other.
What signature logo size works on retina screens?
Export at roughly twice the display size, for example 400 pixels wide for a logo shown at 200. That is a rule of thumb, not a vendor figure, and it helps because high-density screens pack more pixels into each displayed pixel. In Gmail, stay within the published 100-pixel-high maximum, since a 2× export of a tall logo can exceed it. Check on a phone after pasting it in.
Does Smol compress signature images locally?
Yes. Smol runs on your Mac and nothing is uploaded, so your logo and headshots stay private. It outputs PNG or JPG at a quality and maximum dimension you set, and writes a copy beside the original, leaving the original untouched by default.
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