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Offline Developer Tools
Handle common development chores without pasting source data into a remote service. The collection covers JSON, Base64, regular expressions, identifiers, timestamps, colors, and unit conversions.
89 tools
Open a hosted tool or download its standalone version from the main directory.
- JSON FormatterFormat, validate, sort, and minify JSON locally in your browser.
- File HashCalculate SHA-256, SHA-384, or SHA-512 checksums locally.
- Base64 ConverterEncode and decode Unicode text or files as Base64 without uploads.
- Timestamp ConverterConvert local dates, ISO values, and Unix timestamps entirely offline.
- Password GeneratorGenerate strong random passwords locally with the Web Crypto API.
- URL EncoderEncode and decode URL components or complete URLs locally in your browser.
- Markdown PreviewWrite and preview common Markdown formatting locally with a safe HTML export.
- Text DiffCompare two text versions line by line and export a unified diff locally.
- JSON Lines ConverterConvert JSON arrays to JSON Lines and JSONL or NDJSON back to a valid JSON array locally.
- JSON to CSV ConverterConvert JSON arrays to CSV or TSV, align fields, and protect spreadsheet formulas without uploading data.
- IP Range Overlap CheckerCompare existing and planned IPv4 ranges to find overlaps before connecting networks.
- Network Capacity PlannerTurn application demand, concurrency, growth, and utilization targets into a shared uplink requirement.
- Availability & Downtime BudgetCalculate an availability target’s downtime allowance and remaining budget from outage durations.
- TCP Window & BDP CalculatorCalculate bandwidth-delay product and the ideal throughput ceiling imposed by a receive window.
- Optical Link Budget CalculatorCheck minimum receive power, engineering margin, and receiver overload from supplied optical specifications.
- DHCP Pool PlannerRemove gateways, reservations, and exclusions from a LAN scope and check dynamic lease capacity.
- DNS Record Builder & CheckerCreate A, AAAA, CNAME, and MX record lines from a spreadsheet and catch conflicting aliases.
- Firewall Communication Matrix CheckerCompare a spreadsheet of expected traffic decisions with ordered IPv4 rules and export every mismatch.
- Network Configuration DiffCompare ordered configuration lines before and after a change, with original line numbers for review.
- Network Acceptance Test CheckerEvaluate measured loss, latency, jitter, and throughput against explicit per-test acceptance thresholds.
- Interface Counter Delta AnalyzerCalculate per-direction throughput and utilization from two 32-bit or 64-bit octet-counter snapshots.
- IPv4 Subnet CalculatorCalculate network boundaries, masks, host ranges, and /31 point-to-point addresses.
- VLSM Subnet PlannerAllocate non-overlapping LAN subnets from a parent network using required host counts.
- CIDR Aggregator & Range ConverterConvert IPv4 ranges to CIDRs and merge adjacent or duplicate networks without adding addresses.
- CIDR Exclusion CalculatorSubtract IPv4 exceptions from network lists and export the exact remaining CIDRs.
- IP Network Membership CheckerCheck which IPv4 addresses belong to supplied networks, with every matching range shown.
- IPv6 Subnet & Address CalculatorNormalize IPv6 text and calculate prefix boundaries and exact address counts.
- VLAN & IP Plan CheckerCheck a VLAN plan for duplicate IDs, overlapping subnets, and invalid gateway addresses.
- Route Longest Prefix MatchFind the longest matching IPv4 routes and show equally specific next-hop candidates.
- Subnet & Wildcard Mask ConverterConvert between IPv4 prefix lengths, contiguous subnet masks, and inverse wildcard masks.
- MAC Address NormalizerConvert 48-bit MAC addresses to colon, hyphen, and Cisco formats and inspect address bits.
- Network Transfer Time CalculatorEstimate transfer duration from data size, line rate, and assumed effective utilization.
- Required Bandwidth CalculatorCalculate the line rate needed to finish a backup or transfer within a specified window.
- MTU & TCP MSS CalculatorCalculate inner MTU, advertised TCP MSS, and payload budget with explicit encapsulation overhead.
- IPv4 Traffic Rule CheckerEvaluate an IPv4 packet against a simplified ordered rule list and identify the first matching rule.
- tcpdump Capture Filter BuilderBuild validated libpcap filters for protocol, source, destination, and destination ports.
- Network Address RedactorReplace recognized IPv4, IPv6, MAC addresses, and specified hostnames with consistent labels in logs.
- Reverse DNS Name GeneratorGenerate in-addr.arpa and ip6.arpa owner names from IPv4 and IPv6 addresses.
- QR Code Generator & ReaderGenerate QR codes from text or read QR codes from local images without network access.
- Word CounterCount words in multilingual text.
- Line CounterCount total, non-empty, and blank lines.
- UTF-8 Byte CounterMeasure the exact UTF-8 byte size of text.
- Reading Time CalculatorEstimate reading and speaking time from word count.
- Keyword Density CheckerMeasure exact keyword use within a passage.
- Character FrequencyRank visible characters by frequency.
- Word FrequencyRank words by case-insensitive frequency.
- Palindrome CheckerCheck text while ignoring case and punctuation.
- Anagram CheckerCompare two values while ignoring spaces and punctuation.
- Regular Expression TesterList every JavaScript regular-expression match.
- Email ExtractorExtract unique email-like addresses from text.
- URL ExtractorExtract unique HTTP and HTTPS URLs from text.
- Phone Number ExtractorExtract likely international phone numbers for review.
- Hashtag ExtractorExtract unique Unicode hashtags.
- Mention ExtractorExtract unique @mentions from text.
- IPv4 Address ExtractorExtract and validate IPv4 addresses.
- Hex Color ExtractorExtract unique three-, four-, six-, and eight-digit hex colors.
- Duplicate Line FinderReport repeated non-empty lines and their counts.
- Longest Line FinderRank the ten longest lines with their original numbers.
- Text StatisticsSummarize lines, words, characters, bytes, and sentence count.
- UUID v4 GeneratorGenerate cryptographically random UUID version 4 values.
- Nano ID GeneratorGenerate compact URL-safe random identifiers.
- Random Hex GeneratorGenerate secure random hexadecimal tokens.
- Random Integer GeneratorGenerate unbiased integers from zero through one million.
- Dice RollerRoll one or more fair six-sided dice.
- Coin FlipperFlip a virtual fair coin repeatedly.
- Lorem Ipsum GeneratorGenerate temporary Latin-style layout copy.
- Sample Name GeneratorGenerate clearly fictional names for mockups and tests.
- Sample Email GeneratorGenerate reserved example-domain email addresses.
- Color Palette GeneratorGenerate random hex colors for quick visual exploration.
- Random Date GeneratorGenerate ISO dates between 2000 and 2030.
- Sample CSV GeneratorGenerate harmless sample rows for spreadsheet testing.
- Sample JSON GeneratorGenerate a valid JSON array for parser and UI tests.
- Number Sequence GeneratorGenerate a one-based integer sequence.
- Placeholder Slug GeneratorGenerate predictable placeholder slugs for prototypes.
- Binary / Decimal ConverterConvert binary integers to decimal.
- Hex / Decimal ConverterConvert hexadecimal integers to decimal.
- Octal / Decimal ConverterConvert octal integers to decimal.
- Decimal Base ConverterConvert a decimal integer to any base from 2 through 36.
- Roman Numeral ConverterConvert decimal integers from 1 through 3999 to Roman numerals.
- Byte Unit ConverterConvert bytes to binary and decimal storage units.
- Length ConverterConvert meters to common metric and imperial lengths.
- Mass ConverterConvert kilograms to metric and imperial weights.
- Temperature ConverterConvert Celsius to Fahrenheit and Kelvin.
- Area ConverterConvert square meters to common area units.
- Volume ConverterConvert liters to common liquid-volume units.
- Speed ConverterConvert kilometers per hour to other speed units.
- Duration ConverterBreak a duration in seconds into larger units.
- Angle ConverterConvert degrees to radians, turns, and gradians.
- HEX to RGB ConverterConvert a three-, six-, or eight-digit hex color to RGB values.