How to use the RSS Feed Previewer
- Enter the feed address. Paste the address of an RSS or Atom feed. A bare domain path is treated as https. Private and local addresses are refused.
- Read the latest items. The previewer lists up to 200 items with title, link, date, a plain-text summary and any image or enclosure, so you can see what the feed really publishes.
- Pick an item and a network. Choose an item, then switch between X, Threads, Bluesky, Mastodon and Instagram to see the post text, the character count and whether anything was shortened.
- Fix the feed or the template. If titles are empty, dates are missing or summaries are cut in awkward places, fix them at the source feed, then run the preview again.
How the RSS feed previewer works
What it reads
The server downloads the feed once, up to 1 MB, and reads it in a single pass. For each item it keeps the title, the link (for Atom, the alternate link), the date, a plain-text summary taken from description, content or summary, and an image from a media thumbnail, an image enclosure or an image media element.
Dates are shown as given and, when they can be read, as a standard timestamp. Links that do not start with http or https are dropped, so a bad feed cannot hand you a script address.
Sources for the network rules
X: docs.x.com, Counting characters (280 weighted characters, links as 23, emoji as 2). Threads: developers.facebook.com, Threads posts (text up to 500 characters). Bluesky: the app.bsky.feed.post lexicon (300 graphemes). Instagram: developers.facebook.com, Instagram Graph API media (caption up to 2,200 characters). Mastodon: the default 500 character limit, which each server can change. Checked October 2026.
Limitations
This is a preview, not a validator. A feed that renders here can still fail a strict validator, and a feed that fails here may work in a reader that is more forgiving. Feeds that need a login, block automated requests or are larger than 1 MB may be incomplete or fail.
The post text is a starting point. Real posts often get a hand-written hook, and each network may render links, previews and line breaks differently from this approximation.
Frequently asked questions
Which feed formats does the previewer read?
RSS 2.0, Atom and RSS 1.0 (RDF) feeds. It reads title, link, publication date, description or summary, content, enclosures and media thumbnails. JSON Feed is not supported.
Why does it say my address is not a feed?
The address probably returns a web page instead of the feed file. Look for a link labelled RSS or Atom, or a path such as /feed, /rss or /atom.xml. The previewer does not guess feed addresses from a page.
Why are only 200 items shown, and why are summaries short?
To keep the preview fast and safe, the previewer reads at most 1 MB of the feed, shows up to 200 items, cuts titles at 300 characters and summaries at 1,000 characters. Summaries have their HTML removed, so you see plain text.
How is the post text built from a feed item?
The post is the item title, then as much of the summary as fits, then the link. The link is always kept whole. If space is short the summary is dropped first and the title is cut last.
How are characters counted on each network?
X counts every link as 23 characters and gives emoji and CJK characters a weight of 2, within 280. Threads allows 500 characters. Bluesky counts graphemes up to 300. Mastodon defaults to 500 and counts links as 23, though a server can change that. Instagram captions allow 2,200 characters and links in them are not clickable.
Is it safe to enter any address?
The previewer fetches only public http and https addresses. It refuses private, loopback, link-local and cloud-metadata addresses, checks every redirect (at most 3), reads at most 1 MB and gives up after 8 seconds. The feed text is parsed with a single linear pass, never executed, and nothing you enter is stored.