Download Image Using Fetch Api
Bran Cardello
I'm stuck on how exactly to structure the fetch request from the frontend to actually post the data to the S3 url. What options do I use? Guides I read online are making the actual upload request to S3 directly from python, but I'm trying to do it from the frontend to no avail. In my frontend I have a blob of the image, converted to a file. This file is what I'm trying to post to S3. Are there any CORS issues as well?
Fetch is an option for automatically fetching (retrieving) images and videos from existing remote locations and delivering them using dynamic URLs. The files are delivered through a powerful CDN network, greatly improving your users' browsing experience, reducing load on your servers and lowering hosting costs, while you also benefit from on-the-fly image and video transformation and optimization, and all of this with minimum changes on your side.
Fetch enables on-the-fly transformation of remote images and videos with optimized delivery via a CDN. Fetched assets are cached in your Cloudinary product environment for performance reasons. Paid Cloudinary customers can request to have the remote assets checked on a regular basis (every 7 days by default) and if the remote asset has changed, the cached asset is updated accordingly.
This feature supports image and video assets.
Auto-Upload also enables on-the-fly transformation of existing remote assets with optimized delivery via a CDN, while simultaneously uploading the fetched media asset to your Cloudinary product environment for further management, and thus benefiting from a variety of additional features (just like any other asset uploaded to your Cloudinary product environment). After an asset has been auto-uploaded from the remote location, all requests for the asset will reference the asset stored in your Cloudinary product environment. Any further updates to the remote asset will make no difference, as this process does not check for updates.
This feature supports image, video and raw assets.
The fetch feature is a quick way to deliver assets from remote URLs. The asset can be transformed and optimized on the fly, before being cached and delivered through fast, localized CDNs and not via local web servers. To create a fetch URL, simply prepend the following prefix to the URL of the asset:
You can also use the fetch feature to apply any of Cloudinary's image and video transformations to the delivered asset. Simply add the transformation parameters to the URL directly after the fetch prefix and before the URL of the asset.
The following Cloudinary URL delivers an image of Benedict Cumberbatch from Wikipedia that has been transformed as follows: the width and height parameters are both set to 300 pixels, the image is cropped to fill in the new dimensions, retaining the original proportions and setting gravity to the detected face; the image is also made circular by setting the radius parameter to maximum, and finally, depending on the browser/device, the best image format is automatically delivered, optimized and cached via CDN:
URLs containing special characters (particularly the ? character) need to be modified (or escaped) for use with the fetch feature. This is relevant for any special characters that are not allowed "as is" in a valid URL path, as well as other special unicode characters. These URLs should be escaped using % based URL encoding to ensure the URL is valid. Either escape the individual special characters themselves within the URL (for example, replacing ? with %3F) or escape the whole URL.
Note that the methods within Cloudinary's client libraries (e.g. Ruby on Rails cl_image_tag method) automatically perform smart escaping, leaving the URL as simple as possible while escaping certain special characters. Manually escaping URLs as explained here is only relevant when simply adding the fetch prefix to existing URLs.
You can restrict the list of allowed domains that can be used with the fetch feature in the Allowed fetch domains section on the Security page of the Console Settings.
When you fetch a remote asset, a copy of that asset as well as all transformations derived from the remote asset, are cached in your Cloudinary product environment for performance reasons. The following sections describe the available options for deleting and refreshing those assets.
Customers on a paid plan can request full cleanups of all fetched assets that occur at a set time interval. When a cleanup interval is defined, all of your fetched assets, as well as all transformations derived from them, are completely deleted from the cache every X days.
If one of these assets is requested again after the cleanup, it's fetched again from the remote source. This feature is useful for cleaning up your storage in cases where many of your fetched assets become obsolete after a short time period, for example, banner ads.
By default, Cloudinary checks one time after 7 days to see whether the remote images cached in your Cloudinary product environment have changed (by comparing the etag value). If it has changed, the cached image is replaced with the new one, and the next time that image, or a transformation of that asset, is requested, the updated version is delivered.
If you need to apply the new setting to fetched images that have already been delivered, you'll need to delete the relevant fetched images from your product environment. Then, the next time any of those fetched images is requested, it will be re-fetched and the new refresh interval settings will be applied to it.
You can easily display thumbnail images of videos from various public video sites by referencing the unique video identifier used on their site. The cloudinary image delivery URL for the thumbnail follows the format:
It's a brilliant post; you should totally read it. Even if you hate images, uploads and JavaScript. However, there was one thing in there that I didn't want; SuperAgent. It's lovely but I'm a Fetch guy. That's just how I roll. The question is, how do I do the below using Fetch?
Then go to .. to scrape the url .. (put in the above) .. what should show is the designated OG image (same as featured image in this case) .. but what shows up is the logo from the header .. also note that every image on that page is designated by your plug-in as an OG image .. and that should not be the case ..
When a browser parses a web page and begins to discover and download resources such as images, scripts, or CSS, it assigns them a fetch priority in an attempt to download resources in an optimal order. These priorities can depend on the kind of resource and where it is in the document. For example, in-viewport images may have a High priority while the priority for early loaded, render-blocking CSS via s in the could be Very High. Browsers are pretty good at assigning priorities that work well but may not be optimal in all cases.
In this article, we'll discuss the Fetch Priority API and the fetchpriority HTML attribute, which allow you to hint at the relative priority of a resource (high or low). Fetch Priority can help optimize the Core Web Vitals.
Historically, developers have had some, but limited, influence over resource priority using preload and preconnect. Fetch Priority complements these Resource Hints, but it's essential to understand where they all fit in. Preload lets you tell the browser about critical resources you want to load early before they are discovered naturally. This is especially useful for resources that are not easily discovered, such as fonts included in stylesheets, background images, or resources loaded from a script. Preconnect helps warm up connections to cross-origin servers and can help improve metrics like Time-to-first-byte and is useful when you know an origin but not necessarily the exact URL of a resource that will be needed.
Fetch Priority is a markup-based signal (available through the fetchpriority attribute) that developers can use to indicate the relative priority of a particular resource. You can also use these hints via JavaScript and the Fetch API with the priority property to influence the priority of resource fetches made for data. Fetch Priority can also complement preload. Take a Largest Contentful Paint image, which, when preloaded, will still get a low priority. If it is pushed back by other early low-priority resources, using Fetch Priority can help how soon the image gets loaded.
These techniques help to control the browser's priority computation, thereby improving performance and Core Web Vitals. For example, when a critical background image is preloaded, it can be discovered much earlier, improving the Largest Contentful Paint (LCP).
You can provide a Fetch Priority using the fetchpriority HTML attribute. You can use the attribute with link, img, and script tags. The attribute allows you to specify the priority for resource types such as CSS, fonts, scripts, and images when downloaded using the supported tags.The fetchpriority attribute accepts one of three values:
The browser executes fetch with a high priority. If you have multiple fetches that may be fired simultaneously, you can use the high default priority for the more critical data fetches and lower it for less critical data.
Fetch Priority can complement preloads by increasing the granularity of prioritization. If you had already specified a preload as one of the first items in the for an LCP image, then a high Fetch Priority may not result in significant gains. However, if the preload was after other resources, then a high Fetch Priority can improve the LCP. If a critical image is a CSS background image, you should preload it with fetchpriority = "high".
Fetch Priority was first experimented with in Chrome as an origin trial in 2018 and then again in 2021 using the importance attribute. At that time it was known as Priority Hints. The interface has since changed to fetchpriority for HTML and priority for JavaScript's Fetch API as part of the web standards process. To reduce confusion we now refer to this API as Fetch Priority.
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