How to use the Secret Love Letter Card Maker
- Upload a background image in box 1. A photo or a drawing both work, as long as it is a JPG, PNG or WEBP of 10MB or less.
- Type the letter or message you want to hide and press Make card. Check the maximum number of characters shown under the input box.
- Save the finished card as a PNG and send it to the other person as a file (the original), not as a photo.
- The receiver puts the card into box 2 on this site and presses Open card. The picture slowly fades away and the message appears in the result box below.
How text hides inside a picture
A digital image is made of many pixels, and the color of each pixel is set by three values for red, green and blue. Each value is a number from 0 to 255. Changing the last bit of a value to 0 or 1 shifts the color by only one step out of 255, which the eye cannot tell apart. Hiding information inside an image this way is called steganography, and this tool uses it to put text inside a picture.
The text is not stored as it is. It is first turned into bytes and scrambled in several steps with a random value created fresh for every card. Each byte goes through a substitution table, has its bits rotated, and is chained to the result of the previous byte, so the same text gives a different result in every card. The scrambled bits are not stacked at the start of the image but scattered across all the pixels. When opening, the process is run backwards and a check value is verified, so the text is shown only when the card is genuine.
Right after a card is made, the tool opens it once itself to confirm the text comes back unchanged. If that check fails, the card is not handed over and a notice is shown instead, which prevents you from sending a broken card without knowing. Everything happens inside the browser that opened this page, and neither the image nor the text is sent to a server.
Limits to know and ideas for using it
The most important limit is compression that shrinks files. Formats such as JPG throw away tiny differences that the eye does not notice, and the hidden text lives in exactly those tiny differences, so saving as JPG or compressing again destroys it. That is why the card is saved only as a PNG, which keeps values exactly, and why it must be delivered in a way that does not change the original.
When a photo is posted in a messenger, many apps compress it again or change its format to save speed and storage. Even if the picture looks the same, the hidden text is already broken. Attaching it as a file, attaching it to an email or using a cloud sharing link lets the receiver get exactly the same file as the sender. It helps to tell the receiver in advance how to receive it as a file.
A card can be opened only on this site, and because there is no password, anyone who has the card file can open it here. The scrambling method is also custom made, so it differs from encryption verified by experts. That is why this tool suits fun and excitement, such as love letters, birthday messages, proposal events, treasure hunt clues and surprise letters to friends.
On the other hand, do not use it for information that would be a problem if it leaked, such as passwords, ID numbers, bank account numbers or personal contact details. If you need security, use proven encryption software. Also, upload other people's photos or copyrighted images only when you have the right to use them.
Photos with varied colors and texture work well as backgrounds. Nearly flat images can be used too, but the traces are relatively easier to notice, so choosing a meaningful, detailed picture such as a photo of the two of you or a landscape makes the card itself a gift.
There is also a little staging for the moment the card is opened. Press Open card and the picture slowly fades while the text floats up in its place. Recording the screen or reading it together adds to the feeling of the letter. A screenshot cannot make a card file, though, so always keep the saved PNG file.
Tips for using it well
- Keep the saved PNG file exactly as it was made and do not edit it.
- When sending through a messenger, choose file attachment instead of sending as a photo.
- Tell the receiver in advance that the card can be opened only on this site.
- Stay within the limit shown under the input box, and split a long letter into several cards.
- Do not hide sensitive information and use it only for cheerful messages.
FAQ
Why can I not open a card sent through a chat app?
The hidden text lives in tiny differences in the pixel values. When a chat app sends the image as a photo, it often compresses it again or turns it into JPG, which changes those tiny values and breaks the text. Attach it as a file (the original), or send it by email or a cloud link, and it arrives unchanged. Menu names differ from app to app.
Can other people see the text if they look at the card?
To the eye it looks like an ordinary picture and the text is not visible. However, this tool has no password, so anyone who puts the card file into this site can open it. Do not pass the card file to just anyone.
How many characters can I hide?
Up to 500 characters. A very small image holds less, and the maximum for the current image is shown under the input box. Characters that take more space, such as emoji, can fill the limit sooner.
Are my photo and my letter sent to a server?
No. Reading the image, hiding the text and opening a card all happen only inside this browser. The text you enter is not stored anywhere, and the opened message disappears when you load a new card or close the page.
What happens if I crop or screenshot the card?
The text is lost and the card can no longer be opened. The same goes for resizing, cropping, filters, screenshots and saving in another format. Keep and send the card PNG exactly as it was created.
Which images can I use as a background?
JPG, PNG or WEBP files of 10MB or less, at least 100px wide and tall. An image larger than 1600px is reduced with its proportions kept and saved as a PNG card. A transparent PNG is placed on a white background when saved.
Can I hide a password or a bank account number?
Please do not. This tool is for fun, and the way it scrambles text is not a widely proven cipher. Anyone can open a card by putting it into this site, so it is not suited to sensitive information.
Notes & limitations
This is a free tool for fun. There is no password, so anyone who puts the card into this site can open it, and the scrambling method is not verified encryption, so it cannot be used for security or for storing sensitive information. The image and the text you enter are not sent to a server and are processed only in the browser. Editing the card or sending it as a photo can destroy the text.