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Foretaste Get Foretaste

How it works

The file preview extension for Chrome, Edge and Firefox

Foretaste is a free browser extension that opens a file from a link and shows you what is inside, in your own browser, without downloading it first. It works on Chrome, Edge and Firefox, reads over 212 file formats, and never uploads a file anywhere — every parser runs inside the extension on your own machine.

Right-click any file link and choose Open with Foretaste. A panel opens over the page. Read it, then decide whether you want to download it — or close it and carry on.

Add to Chrome, free Add to Edge, free Add to Firefox, free

01

Why this has to be an extension

An ordinary web page cannot read a file from another website. That is not an oversight, it is the rule browsers are built on, and it is why every free tool in this category asks you to upload the file first: the file has to be on your machine before their page can touch it.

An extension is the one thing a browser will grant that permission to, and only for the sites you name. So Foretaste can fetch the file from where it already is, which means it never has to be anywhere else.

How you use it

  1. Install it. Your browser asks for website access once.

    At install, for the access that lets it fetch a file, and there is no second prompt and nothing to grant per site. Your browser's own extension settings are where you narrow or withdraw it later. What it does and does not buy.

  2. Right-click the file link and choose "Open with Foretaste".

    Or press the small marker Foretaste puts beside file links, which you can turn off everywhere or on the sites you choose. Either way it is one action, with no dialog asking what you meant.

  3. Or drop a file straight onto the reader.

    A file already on your machine, or a link you have copied, dropped anywhere on the Foretaste tab, opens in the same reader with the same formats. No site permission is involved, because nothing is being fetched from anywhere.

  4. Read it, then decide.

    The file opens in a panel over the page, or in a new tab if you prefer that. Save it to disk or close it and carry on. Saving works on every format, including the ones Foretaste cannot open, and it needs no site permission at all.

releases · example.org

Downloads / 2026 / Course materials

Hover or tap the marker and Foretaste says what the file is, without fetching a single byte of it. Everything on that card was already on the page.

02

What it opens

212 file extensions. These four are where most people arrive, and each has a page saying what you actually get and where it stops:

  • Office documents. Word, Excel and PowerPoint drawn in the tab, without desktop software. What each of the three shows.
  • Archives. ZIP, TAR, GZIP, 7z and RAR listed as a folder tree, and one file opened from inside. A ZIP keeps its index at the end, so listing a 40 MB archive costs about 67 KB. How the ranged read works.
  • Databases and datasets. SQLite schemas out of the first 256 KB, and Parquet row counts and column types out of the footer.
  • Text, code and media. CSV a page at a time, JSON as a tree, logs filtered by level, images with their Exif, audio and video streamed from the original address.

The full list of all 212 extensions, each row with its limits.

field-readings.csv

field-readings.csv

Table1.4 MBRows 18,402Columns 6

Read 64 KB of 1.4 MB 4.5%

Read 64 KB of 1.4 MB, one page at a time.

Processed locally · Foretaste reads files on your device and does not upload them.

# taken_at site temp_c humidity sky
1 2026-03-02 09:14 north ridge 11.4 82 clear
2 2026-03-02 09:41 north ridge 11.9 80 clear
3 2026-03-02 10:03 beck crossing 9.8 91 drizzle
4 2026-03-02 10:55 beck crossing 9.6 93 drizzle
5 2026-03-02 11:20 south tarn 12.2 77 cloud

A million-row file turns a page at a time, and the last page costs what the first one did.

manifest.json

manifest.json

Structured data8 KBKeys 14

The whole file was read - 8 KB.

Processed locally · Foretaste reads files on your device and does not upload them.

{
  "manifest_version": 3,
  "name": "Foretaste",
  "permissions": [
    "contextMenus",
    "downloads",
    "storage"
  ],
  "host_permissions": ["<all_urls>"],
  "background": {
    "service_worker": "background.js",
    "type": "module"
  }
}

Folded as a tree, or read as text. Either way it is parsed in your tab.

server.ts

server.ts

Code4 KBTypeScript

The whole file was read - 4 KB.

Processed locally · Foretaste reads files on your device and does not upload them.

/* The index lives at the end. Ask for the end. */
export async function listZip(read: Read, size: number) {
  const tail = await read(Math.max(0, size - 65557), size);
  const end = findEndOfCentralDirectory(tail);
  if (!end) throw new Error('no central directory');
  return parseEntries(await read(end.offset, end.offset + end.size));
}

Thirty-six grammars, coloured with the product's own six inks rather than a stock theme.

orders.sqlite

orders.sqlite

SQLite database512 MBTables 3

Read 12 KB of 512 MB 0.00%

Read 12 KB of 512 MB: the header and the schema pages.

Processed locally · Foretaste reads files on your device and does not upload them.

Tables

  • customers 6 columns
  • orders 9 columns
  • order_items 5 columns

Half a gigabyte, and the schema of all of it came out of one range read. Counting the rows exactly walks every table, so that is a button.

lecture-03.srt

lecture-03.srt

Subtitles22 KBCues 418

The whole file was read - 22 KB.

Processed locally · Foretaste reads files on your device and does not upload them.

  1. 00:00:04,120 → 00:00:07,880 Right, so the index lives at the end of the file.
  2. 00:00:08,010 → 00:00:12,400 Which means you can read it without touching the rest.
  3. 00:00:12,600 → 00:00:15,970 That is the whole trick, and it is in the format spec.

Readable as text before you decide whether the track is the right one for the film.

Inter-Variable.woff2

Inter-Variable.woff2

Font96 KBVariable

The whole file was read - 96 KB.

Processed locally · Foretaste reads files on your device and does not upload them.

Sphinx of black quartz, judge my vow

ABCDEFGHIJKLMNOPQRSTUVWXYZ

abcdefghijklmnopqrstuvwxyz 0123456789

Drawn with the browser's own FontFace, so it is the real face rather than a picture of it.

README.md

README.md

Markdown3 KB

The whole file was read - 3 KB.

Processed locally · Foretaste reads files on your device and does not upload them.

Field trip, autumn term

Readings were taken every twenty minutes at three sites. The raw dumps are in raw/ and the cleaned series is data/readings.csv.

  • North ridge, exposed, wind above 20 km/h all morning
  • Beck crossing, sheltered, drizzle from 10:00
  • South tarn, open water, cloud clearing by noon

Headings, lists, links and code, drawn rather than shown as the characters that made them.

thesis-draft.pdf

thesis-draft.pdf

PDF284 MBPages 312

Read 1.9 MB of 284 MB 0.67%

Read 1.9 MB of 284 MB: the index, then this page.

Processed locally · Foretaste reads files on your device and does not upload them.

A PDF keeps its cross-reference table at the end, which is the property a ZIP has, so Foretaste’s own engine fetches the index and then only the ranges a page needs. The browser’s viewer takes every byte before it draws page one.

report-final.docx

report-final.docx

Document1.7 MBPages 356A4

The whole file was read - 1.7 MB.

Processed locally · Foretaste reads files on your device and does not upload them.

Autumn term report

Readings were taken at three sites every twenty minutes between 09:00 and 12:00. The north ridge was exposed for the whole morning and the beck crossing had drizzle from ten.

Nothing in the series suggests the sensor drifted, and both gaps are accounted for in raw/notes.txt.

Drawn on measured pages at the sheet size and margins the file states, rather than poured into one long column. 356 pages of the reference document in 713ms.

invite.ics

invite.ics

Calendar2 KBEvents 1

The whole file was read - 2 KB.

Processed locally · Foretaste reads files on your device and does not upload them.

Event Autumn term planning
When Thursday 8 October, 14:00 to 15:30
Where Room B204, and a video link
Organiser timetabling@example.ac.uk
Guests 6 invited, 4 accepted

Read, and not accepted. Nothing is added to any calendar, because nothing hands the file to a calendar application.

receipt-scan.jpg

receipt-scan.jpg

Picture2.4 MB3024 × 4032

The whole file was read - 2.4 MB.

Processed locally · Foretaste reads files on your device and does not upload them.

Text read out of it

HARDWARE AND TOOLS · 14 BRIDGE STREET
2026-03-02 · 11:42 · till 3
Drill bit set, 5 pc — 18.99
Masking tape, 50m — 4.25
Total — 23.24

Recognised on this machine, with no network request at all. English ships inside the extension; another language is one download you ask for.

No file is uploaded, because there is nowhere to upload it to

Every parser runs inside the extension. Foretaste has no file-processing server, no analytics, no telemetry and no crash reporting, and a check in the build script fails the release if any network call other than fetch, or any hardcoded address outside a short allowlist, appears in the built output.

Exactly what Foretaste can and cannot see, including every request it is capable of making.

03

Where you can install it

Desktop browsers. Chrome extensions do not run on Chrome for Android, which is Google's limitation rather than ours, and Firefox for Android is not claimed until it has been tested on one.

04

The rest of it, by what you came for

The questions people ask

What does a file preview extension do?

It reads a file straight from its link and shows you what is inside, instead of saving it to your machine first. Foretaste puts an "Open with Foretaste" entry on the right-click menu of any file link and draws the file in a panel over the page.

Does Foretaste upload files to a server to preview them?

No. Every parser runs inside the extension, on your own machine. There is no Foretaste server for a file to go to, and a check in the build fails the release if any hardcoded address outside a short allowlist appears in the output.

Which browsers is Foretaste available on?

Chrome, Edge and Firefox, each from its own store, and free on all three. The Firefox add-on is a separate Manifest V2 build of the same code.

How can I open a file without downloading it?

Install Foretaste on Chrome, Edge or Firefox. Then right-click any file link on any website and choose "Open with Foretaste". The file is fetched from the original server and read inside a browser tab. Nothing is saved to your device unless you explicitly choose to save it.

Can I preview files in my browser without installing desktop software?

Yes. Foretaste is a browser extension that reads over 212 file formats directly in the browser. It does not need Microsoft Office to open a Word or Excel file, nor Adobe Reader for PDFs. Every parser is built into the extension itself and runs on your own machine.

Is there a free Chrome extension to preview files before downloading?

Foretaste is free on Chrome, Edge and Firefox. Reading any file in the browser is free with no account required. The paid plan raises the size limits on text files, spreadsheets and databases, and lets you save individual files out of a remote archive.

What file types can Foretaste open without downloading?

Foretaste reads over 212 file extensions: documents (DOCX, PDF, ODT), spreadsheets (XLSX, CSV, ODS), archives (ZIP, RAR, 7z, TAR, GZIP), code and data files (JSON, XML, YAML, SQL), images (JPG, PNG, WebP, SVG, AVIF), audio and video (MP3, MP4), databases (SQLite, Parquet), e-books (EPUB), fonts (TTF, WOFF), subtitles (SRT, VTT), calendars (ICS) and contact cards (VCF).