Prepare images for the web
Scale photos to their display size, switch to WebP, then compress so pages load faster.
Images, PDFs, data.
Handled right on your device.
Salary and tax calculators, lunar calendar, image compression, PDF merging, QR codes and nearly 80 more tools, done in seconds. Nothing to install, no account, files never uploaded.
JPG, PNG, WebP, GIF, BMP, AVIF, PDFFiles stay on your device
Drop images or PDFs here
We recognise the file type and suggest the right tool. You can also paste an image with Ctrl+V anywhere on the page.
- tools ready to use
- 79
- files sent to a server while processing
- 0
- cost, no account needed
- $0
- languages: Vietnamese and English
- 2
All tools
Every tool comes with a guide, reference tables and FAQs right below the workspace.
PDF & Image
17 tools- Image CompressorShrink JPG, PNG and WebP files while keeping them sharp.
- JPG, PNG & WebP ConverterConvert images between JPG, PNG and WebP in bulk.
- Image ResizerResize images by pixels or percentage while keeping the aspect ratio.
- Merge PDFCombine several PDFs into one, reorder them and pick the pages you need.
- Image to PDFTurn JPG, PNG and WebP images into one PDF with your choice of page size and margins.
- Crop ImageNewCrop photos freely or to 1:1, 16:9, 4:3 and ID-photo sizes, with exact pixel input.
- Rotate & Flip ImageNewRotate photos 90°, 180° or any angle, or mirror them; many images at once, ZIP download.
- Split PDFNewSplit a PDF by page ranges, into single pages, every N pages, or extract chosen pages.
- PDF to JPG / PNGNewTurn each PDF page into a JPG or PNG image at 72, 150 or 300 DPI, with ZIP download.
- HEIC to JPGNewConvert iPhone HEIC and HEIF photos to JPG or PNG that open everywhere.
- Watermark ImageNewStamp text or a logo on many photos at once: set position, opacity, angle, or tile it across the image.
- Image CollageNewCombine several photos into one: side by side, stacked or in a grid, with spacing, borders and background.
- Organize PDF PagesNewReorder, rotate, delete or duplicate PDF pages, or insert blank pages, right on the thumbnails.
- Add Page Numbers to PDFNewPrint page numbers on a PDF: choose the position, a style like “1 / 10”, the first number, skip the cover.
- Favicon GeneratorNewMake favicon.ico, apple-touch-icon, 192/512 icons and the HTML tags from an image, SVG logo or letters.
- Image Color PickerNewClick a photo to get the HEX, RGB and HSL code, plus a palette of the main colours pulled from it.
- EXIF Viewer and RemoverNewSee the hidden data in a photo (camera, date taken, GPS location) and strip it before you share.
Finance & Business
11 tools- Percentage CalculatorPercent of a number, percentage ratios and percent change, with the formula.
- Gross ↔ Net Salary CalculatorNewConvert Vietnamese gross salary to net and back: insurance, family deductions and 2026 income tax.
- Vietnam Personal Income Tax CalculatorNewWork out Vietnamese personal income tax on salary, monthly or for the year, with the 2026 brackets.
- Savings Interest CalculatorNewWork out term-deposit interest by term, paid at maturity or monthly, with rollovers and compounding.
- Loan Repayment CalculatorNewBuild a home or car loan schedule: declining balance or equal payments, promo rates, grace period.
- Number to wordsNewSpell out numbers and đồng amounts in Vietnamese or English, up to trillions.
- VAT calculatorNewAdd or extract VAT at 0, 5, 8 or 10% across several line items, with totals.
- Profit margin calculatorNewProfit, margin and markup, the price for a target margin, and stacked discounts.
- Compound Interest CalculatorNewCompound interest with monthly, quarterly or yearly contributions, a growth chart, inflation and the rule of 72.
- Exchange Rate ConverterNewToday's Vietcombank rates (cash, transfer, selling) and conversion between VND, USD, EUR, JPY and more.
- Electricity Bill CalculatorNewVietnam household electricity bill by EVN tiers, from kWh or meter readings, with VAT.
Everyday utilities
12 tools- BMI calculatorNewWork out your BMI on WHO and Asian cut-offs, plus a healthy weight for your height.
- Date calculatorNewDays between two dates, working days, adding or subtracting dates, and exact age.
- Vietnamese Lunar CalendarNewConvert between solar and Vietnamese lunar dates, with stem-branch names, solar terms and lucky hours.
- Random PickerNewDraw random numbers, pick names, split teams, flip coins and roll dice.
- Unit ConverterNewConvert length, weight, area, volume, temperature, speed, data and time.
- Countdown & StopwatchNewCountdown timer with alarm, lap stopwatch and days-until-event counter.
- Split Bill CalculatorNewSplit a bill equally, by shares or by items, with fees and VAT, and see who pays whom.
- Due Date CalculatorNewEstimate your due date from your last period, conception or an ultrasound, with today's gestational age and milestones.
- Calorie Calculator (BMR, TDEE)NewBMR, TDEE and daily calories to lose, keep or gain weight, with a suggested protein, fat and carb split.
- Vietnamese Zodiac & ElementNewFind the lunar year, zodiac animal and nạp âm element of a birth date, plus Vietnamese age.
- Time Zone ConverterNewConvert times between cities with daylight saving handled, and find a meeting time that suits all.
- Grade Average & GPA CalculatorNewSemester and year averages under Vietnam's Circular 22, overall ratings and university GPA.
Text tools
8 tools- Word & Character CounterCount words, characters, sentences and paragraphs; estimate reading time and SMS parts.
- Case Converter & Accent RemoverNewSwitch to UPPERCASE, lowercase, Title or Sentence case; strip Vietnamese accents and tidy spaces.
- Text CompareNewCompare two texts line by line or word by word, with additions in green and deletions in red.
- Vietnamese Font ConverterNewFix garbled Vietnamese: convert TCVN3 (.VnTime) and VNI to Unicode and back, with auto-detection.
- Sort Lines and Remove DuplicatesNewSort a list A–Z, by number or length, reverse or shuffle it, and remove duplicate or empty lines.
- Find and Replace TextNewReplace many pairs at once, whole words, accent-insensitive or regex, with highlighted matches and undo.
- Text to Speech ReaderNewListen to Vietnamese or English text with your device's voices: speed, pitch, pause and resume.
- Lorem Ipsum GeneratorNewGenerate Lorem Ipsum or Vietnamese placeholder text by paragraphs, sentences or words, as text or HTML.
Developer
16 tools- JSON Formatter & ValidatorFormat, minify and validate JSON, pinpointing the exact line and column of errors.
- Base64 Encoder & DecoderEncode and decode Base64 for UTF-8 text and files, with Base64URL support.
- Password GeneratorNewRandom passwords or memorable passphrases, with strength in bits.
- URL Encode & DecodeNewPercent-encode and decode URLs, edit query parameters, convert IDN to Punycode.
- Hash GeneratorNewMD5, SHA-1, SHA-256 and SHA-512 hashes and HMAC for text and files, plus checksum check.
- UUID GeneratorNewBulk UUID v4 and v7 with formatting options, plus a decoder for version and timestamp.
- Unix Timestamp ConverterNewConvert Unix timestamps to dates and back; auto-detects seconds, ms and µs.
- Color ConverterNewConvert HEX, RGB, HSL, HSV and CMYK; check WCAG contrast; get tints and shades.
- User-Agent ParserNewParse a User-Agent into browser, OS, device and bots like Google, Bing or AI.
- Regex TesterNewTest regular expressions with highlighted matches, groups, replace and a plain-English breakdown.
- JWT DecoderNewRead a JWT's header and payload, check its expiry and verify HS, RS, PS and ES signatures.
- JSON ↔ CSV, YAML, XML ConverterNewTurn JSON into Excel-ready CSV and back, convert JSON ↔ YAML and JSON to XML.
- Cron Expression ExplainerNewTurn a cron expression into plain English, see the next 10 runs in any time zone and build one fast.
- Number Base ConverterNewConvert between binary, octal, decimal, hex and any base 2–36, with two's complement and text ↔ binary.
- HTML Entity EncoderNewTurn < > & " and accented letters into < é… or decode them back, with a table of common entities.
- Chmod CalculatorNewTick read, write and execute boxes to get chmod numbers like 755 or 644 and rwxr-xr-x, with ready commands.
Network & Hosting
8 tools- IPv4 Subnet CalculatorNetwork and broadcast address, host range, subnet mask and subnetting.
- What Is My IPNewSee your public IPv4 / IPv6 address, browser, OS, language and time zone.
- DNS LookupNewCheck A, AAAA, CNAME, MX, NS, TXT, SOA and CAA records, plus SPF and DMARC.
- IPv6 Subnet CalculatorNewIPv6 range, address count, address type and subnetting into /48, /56, /64.
- IP Address ConverterNewConvert IPs to integer, hex, binary, octal, IPv4-mapped IPv6 and back.
- IP Range to CIDRNewTurn IP ranges into CIDR blocks, merge lists and check which block an IP is in.
- SSL CheckerNewCheck a domain's SSL certificate: issuer, expiry date, SAN names, chain and TLS.
- HTTP Header CheckerNewSee the status code, redirect chain, HTTP headers and a security-header score.
Marketing & SEO
7 tools- QR Code GeneratorCreate QR codes for links, text, Wi-Fi, email and phone; download PNG or SVG.
- Slug GeneratorNewTurn titles (including Vietnamese) into clean SEO-friendly URL slugs: no accents, hyphens, lowercase.
- UTM BuilderNewAdd utm_source, utm_medium and utm_campaign to links to track each channel in Google Analytics.
- Barcode GeneratorNewCreate EAN-13, EAN-8, UPC-A, Code 128, Code 39 and ITF-14 barcodes with check digits; PNG, SVG, ZIP.
- Google SERP Snippet PreviewNewSee how your title and description look on Google desktop and mobile, with pixel width and truncation.
- Meta Tag GeneratorNewGenerate title, description, canonical, Open Graph, Twitter Card, hreflang and JSON-LD with share previews.
- Keyword Density CheckerNewCount words and 1–3 word keyword density in an article, and check the focus keyword in titles and headings.
What do you need to do?
The most common jobs and the quickest way to get them done.
| Task | Tool | Tip |
|---|---|---|
| You got a gross salary offer and want the take-home pay | Gross ↔ Net Salary Calculator | Pick the right minimum-wage region and number of dependants; every deduction is broken down. |
| Check today's lunar date and how long until Tết | Vietnamese Lunar Calendar | Converts both ways, with can chi and leap months. |
| iPhone .HEIC photos won't open on your computer | HEIC to JPG | Convert many photos at once and download a ZIP. |
| You only need to send a few pages of a long PDF | Split PDF | Enter ranges like 1-3, 7 or pick pages on the thumbnails. |
| An upload form says your photo is too large | Image Compressor | Drag “Compression level” to about 60% and cap the long edge at 1,920 px. |
| Turn photos of both sides of an ID into one PDF | Image to PDF | A4, automatic orientation, small margin. |
| Combine a contract and its appendix | Merge PDF | “Pages” accepts ranges like 1-3, 5, 8-. |
| Square 1080 × 1080 product photos | Image Resizer | Unlock the ratio and choose “Crop to fill”. |
| Turn a heavy PNG into JPG or WebP | JPG, PNG & WebP Converter | WebP is usually smaller and keeps transparency. |
| A Wi-Fi QR code for your counter | QR Code Generator | Pick the Wi-Fi type and print it at least 3 cm wide. |
| Check SEO title, description and SMS length | Word & Character Counter | Messages with accents fit only 70 characters per SMS. |
| What is 30% off, or how much did sales grow | Percentage Calculator | Every result shows the formula with your numbers. |
| Find the broken line in an API response | JSON Formatter & Validator | “Go to error” jumps straight to the problem. |
| Embed an image as a string in HTML / CSS | Base64 Encoder & Decoder | Use the File tab with data URI turned on. |
| Split a /24 network for four teams | IPv4 Subnet Calculator | Use “Subnetting” by number of subnets. |
Suggested workflows
Combine tools to finish a whole task.
Assemble documents for online forms
Snap paperwork with your phone, turn the photos into a PDF and merge it with your other PDFs.
Publish and print
Check title, description and message length, then generate a QR code that links to your post for print.
Work with APIs
Pretty-print and validate JSON responses, decode Base64 strings in tokens or payloads.
Where do your files go?
Nowhere. Every tool on the site runs in JavaScript right inside your browser.
- 1
You pick a file
Your browser reads it from your computer or phone. The site never receives its contents.
- 2
Processed on your device
Heavy work (compression, PDF merging, large JSON) runs in a Web Worker so the page stays responsive.
- 3
Download the result
The result is created in browser memory; download it or pass it on to another tool.
- When you pass a result to another tool, it is kept briefly in your browser's own IndexedDB and removed once used (10 minutes at most).
- Closing the tab discards everything being processed. No copy exists on a server.
- The server only keeps ordinary technical logs (IP address, pages visited) for operations and security.
What is Công Cụ Nhanh?
Công Cụ Nhanh (congcunhanh.com, Vietnamese for “quick tools”) is a free collection of online tools: compress and convert images, merge PDFs, turn images into PDF, create QR codes, count words, calculate percentages, format JSON, encode Base64 and calculate IPv4 subnets.
Every tool runs right in your browser: images, documents and text are never uploaded, there is nothing to install and no account to create, and it works on phones as well as desktops.
Your files stay on your device
Images, PDFs and text are processed right in your browser. Nothing is uploaded or stored, so it is safe for personal documents.
Free, no account needed
No sign-up, no usage limits and no watermark on your results.
Fast, even on mobile
A lightweight interface that only loads what each tool needs, so it works well on mobile data.
Accurate and explained
Clear error messages and formulas shown alongside results so you can verify them yourself.
Frequently asked questions
Is Công Cụ Nhanh free?
Yes. Every tool is free with no usage limits, no sign-up and no watermark on your results.
Are my files uploaded to a server?
No. Images, PDFs and text are processed with JavaScript in your browser; the site never receives or stores your file contents.
Does it work on mobile?
Yes. The interface is built for small screens, and you can pick files straight from your photo library or Files app.
How large can files be?
It depends on the tool: images up to 25 MB each (30 at a time), PDFs up to 100 MB each and 300 MB per merge, JSON and Base64 up to 10 MB.
Which tools are available?
There are 79 tools in 5 categories: PDF & Image (compress, convert JPG/PNG/WebP, resize, merge PDF, image to PDF), Finance (percentage calculator), Developer (JSON, Base64), Network (IPv4 subnet calculator) and Marketing & SEO (QR codes, word counter).
PDF & ImageFinance & BusinessEveryday utilitiesText toolsDeveloperNetwork & HostingMarketing & SEO