I have a habit of building small side projects. Couple of them are KeyVal.org and ArrayList.org. None of them require API authentication.
KeyVal.org as the name says it simple key:value db.
ArrayList.org is a REST API service for creating lists and adding elements to them.
You can create a unique list by visiting Arraylist.org. Click on 'Create List', and it will generate a unique list for you and provide you with two URLs.
One to add elements to your new list.
Second url to see the elements from that list.
Important: Don't forget to store the second url, it contains a password to read.
Use Case: Email subscription form. One good use case is a user subscription form. Let's say you have a "coming soon" page and you want to add an email subscription form.
ArrayList can collect your emails without needing a backend API or database.
A sample HTML Form and Javascript code. Remember to replace the action url with your own list url.
<html>
<body>
<iframe name="dummyframe" id="dummyframe" style="display: none;"></iframe>
<form name="emailform" action="https://api.arraylist.org/add/7nmldtl6e2/" target="dummyframe" >
<label for="fname">Email:</label><br>
<input type="text" id="email" name="email" value="">
<input type="submit" value="Submit">
</form>
<script>
let eform = document.forms["emailform"];
eform.addEventListener("submit", (e) => {
alert("Thank You");
});
</script>
</body>
</html>
You can retrieve your form submissions with the second password URL. Let me know if you need any additional features.