Developer error index
Developer Troubleshooting
Find focused explanations for common parser, validation, encoding, token, timestamp, identifier, and hashing problems, then open the matching browser-local tool to reproduce or fix the issue.
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252 troubleshooting pages
JSON troubleshooting
JSON problems
Diagnose JSON parser errors, malformed payloads, escaping mistakes, truncated responses, and JavaScript values that are not valid JSON.
- Unexpected End of JSON Input – Causes and Fixes
- Unexpected Token in JSON – Find the Error
- Unexpected Token < in JSON – Why It Happens
- JSON Trailing Comma – Find and Fix It Online
- Single Quotes in JSON – Convert to Valid JSON
- Unquoted JSON Keys – Add Required Quotes
- Comments in JSON – Remove Invalid JSON Comments
- Missing Comma in JSON – Find and Fix It
- Missing Colon in JSON – Locate the Syntax Error
- Missing Closing Brace in JSON – Find and Fix }
- Missing Closing Bracket in JSON – Find and Fix ]
- Invalid Escape in JSON – Find Bad Backslashes
- Unexpected Token o in JSON – Causes and Fixes
- Unexpected Token u in JSON – Why JSON.parse Fails
- Unexpected Non-Whitespace Character After JSON – Fix Extra Data
- Expected Property Name in JSON – Causes and Fixes
- Expected Comma or Closing Brace in JSON – Fix Object Syntax
- Expected Colon After Property Name in JSON – Find the Error
- Unterminated String in JSON – Find the Missing Quote
- Unescaped Newline in JSON – Escape Line Breaks Correctly
- Unescaped Quotes in JSON – Escape Double Quotes Correctly
- Bad Control Character in JSON – Find Invalid String Characters
- Bad Unicode Escape in JSON – Fix \uXXXX Errors
- Leading Zero in JSON Number – Why 01 Is Invalid
- JSON.parse Empty String – Why It Fails and What to Do
- JSON.parse(undefined) – Why It Fails and How to Fix It
- HTML Response Instead of JSON – Diagnose API Parse Errors
- Truncated JSON – Detect and Fix Cut-Off JSON Data
- Multiple JSON Objects – Fix Concatenated JSON or Use JSONL
- Double-Encoded JSON – Detect and Decode JSON Stringified Twice
- Escaped JSON String – Decode Backslash-Escaped JSON Safely
- JSON with UTF-8 BOM – Find and Handle the Invisible BOM
- JavaScript Object vs JSON – Syntax Differences and Fixes
- NaN in JSON – Why It Is Invalid and How to Handle It
- Infinity in JSON – Handle Infinity and -Infinity Safely
- undefined in JSON – Why It Is Invalid and How to Replace It
YAML troubleshooting
YAML problems
Trace YAML indentation, mapping, sequence, quoting, directive, anchor, alias, and flow-style errors with parser-focused examples.
- YAML Indentation Error – Find and Fix Invalid Indentation
- Tabs in YAML – Fix Tab Indentation Errors
- Duplicate Keys in YAML – Find Repeated Mapping Keys
- Mapping Values Are Not Allowed Here – YAML Error Fix
- Could Not Find Expected ':' – YAML Error Fix
- Expected <block end> – YAML Indentation Error Fix
- YAML Sequence Indentation Error – Fix List Indentation
- YAML Multiline String Indentation – Fix Block Scalar Errors
- Invalid Escape Sequence in YAML – Fix Double-Quoted Strings
- Unclosed Quoted String in YAML – Find Missing Quotes
- YAML Reserved Character Error – Quote @ and Backtick Values
- Multiple YAML Documents Error – Fix Unexpected --- Separators
- YAML Flow Sequence Missing Comma – Fix [ ] Lists
- YAML Flow Mapping Missing Comma – Fix { } Objects
- Invalid YAML Alias – Fix Malformed *anchor References
- YAML Multiline Implicit Key – Keep Flow Keys on One Line
- Undefined Alias in YAML – Fix Missing Anchor References
- Missing YAML Anchor Name – Fix Bare & Anchor Syntax
- Unclosed YAML Flow Sequence – Fix Missing ] Brackets
- Unclosed YAML Flow Mapping – Fix Missing } Braces
- Invalid YAML Block Scalar Header – Fix | and > Indicators
- YAML Directive Missing --- Document Start – How to Fix
- Content After YAML ... Document End – Start a New Document
- Duplicate %YAML Directive – Remove Repeated YAML Version Directives
XML troubleshooting
XML problems
Find XML well-formedness problems involving tags, attributes, entities, namespaces, declarations, CDATA, comments, and root structure.
- XML Mismatched Tag – Find Opening and Closing Tag Errors
- XML Unclosed Tag – Find Missing Closing Tags
- Multiple Root Elements in XML – Fix Extra Top-Level Elements
- Unescaped Ampersand in XML – Fix & Entity Errors
- Unescaped Less-Than Sign in XML – Fix < in Text
- Duplicate XML Attribute – Fix Repeated Attribute Names
- Unquoted XML Attribute Value – Fix Missing Attribute Quotes
- Unclosed XML Comment – Fix Missing --> Comment Endings
- Undefined XML Entity – Fix Entity Not Defined Errors
- XML Entity Missing Semicolon – Fix EntityRef Errors
- Invalid XML Character Reference – Fix Numeric Entity Errors
- Invalid XML Element Name – Fix Start Tag Name Errors
- Undeclared XML Namespace Prefix – Fix Prefix Not Defined Errors
- Unclosed XML CDATA Section – Fix Missing ]]> Errors
- Double Hyphen in XML Comment – Fix Invalid -- Comment Syntax
- XML Declaration Not at Start – Fix Declaration Position Errors
- Text Before XML Root Element – Fix Content Before the Root Tag
- Text After XML Root Element – Fix Trailing Content Errors
- XML Attribute Missing Equals Sign – Fix name"value" Syntax
- Unescaped Quote in XML Attribute – Fix Broken Attribute Values
- Extra Closing Tag in XML – Remove Unexpected End Tags
- XML DOCTYPE After Root Element – Move DOCTYPE to the Prolog
- Unclosed XML Processing Instruction – Fix Missing ?> Terminators
- CDATA End Marker ]]> in XML Text – Fix Invalid Character Data
CSV troubleshooting
CSV problems
Debug CSV delimiter, quoting, header, row-width, empty-cell, multiline-field, and type-preservation issues before importing tabular data.
- CSV Inconsistent Column Count – Find Rows with Missing or Extra Fields
- CSV Unclosed Quoted Field – Fix Missing Closing Quotes
- Quote in Unquoted CSV Field – Fix Quotes That Start Mid-Field
- Character After Closing Quote in CSV – Fix Trailing Text After Quoted Fields
- Blank Line in CSV – Fix Empty Records That Break Column Counts
- Multiline CSV Field Not Quoted – Fix Newlines That Split Records
- Empty CSV Header – Fix Blank Column Names Before CSV to JSON
- Duplicate CSV Header – Fix Repeated Column Names Before CSV to JSON
- Extra CSV Delimiter – Fix Rows with Too Many Columns
- Missing CSV Delimiter – Fix Rows with Too Few Columns
- Unquoted Comma in CSV Field – Keep Commas Inside One Cell
- Trailing CSV Delimiter – Remove Accidental Empty Final Columns
- Space After Closing CSV Quote – Fix Strict CSV Parsing Errors
- Unescaped Quote in CSV Field – Escape Double Quotes Correctly
- Whitespace-Only CSV Header – Fix Blank Keys Before CSV to JSON
- Duplicate CSV Headers After Trimming – Fix Whitespace Key Collisions
- CSV to JSON Missing Header – Stop the First Data Row Becoming JSON Keys
- CSV Header Only – Why CSV to JSON Returns an Empty Array
- Empty CSV Cell to JSON – Why Blank Cells Become Empty Strings
- Empty CSV Row to JSON – Why a Blank Record Becomes an Object of Empty Strings
- CSV to JSON Numbers as Strings – Why Numeric-Looking Cells Stay Quoted
- CSV to JSON Boolean Values as Strings – Why true and false Stay Quoted
- CSV Leading Zeros to JSON – Preserve IDs Like 00123 Without Numeric Coercion
- CSV Header Whitespace – Why CSV to JSON Trims Spaces Around Property Names
Regex troubleshooting
Regex problems
Troubleshoot JavaScript regular-expression syntax, flags, anchors, quantifiers, groups, lookarounds, matching behavior, and replacements.
- Regex Unclosed Group Error – Fix Unterminated Parentheses
- Regex Unclosed Character Class – Fix Unterminated [ ]
- Regex Range Out of Order – Fix Invalid Character Range
- Regex Nothing to Repeat Error – Fix Leading Quantifiers
- Regex Invalid Quantifier Range – Fix {min,max} Order
- Regex Backslash at End of Pattern – Fix Incomplete Escape
- Regex Duplicate Flag Error – Remove Repeated g, i, m Flags
- Regex Invalid Flag Error – Fix Unsupported JavaScript Flags
- Regex Match Whole String – Add Start and End Anchors
- Regex Escape Dot – Match a Literal Period Instead of Any Character
- Regex Case Insensitive Match – Use the JavaScript i Flag
- Regex Word Boundary – Stop Matching Inside Longer Words
- Regex Alternation Precedence – Group OR Patterns with Anchors
- Regex * Matches Empty String – Use + When One Is Required
- Regex Multiline Anchors – Use the JavaScript m Flag
- Regex Dot Does Not Match Newline – Use the JavaScript s Flag
- Regex Capture Groups – Inspect Numbered Captures Online
- Regex Named Capture Groups – Use (?<name>...) in JavaScript
- Regex Non-Capturing Group – Use (?:...) Without Extra Captures
- Regex Greedy vs Lazy Quantifiers – Compare .* and .*?
- Regex Positive Lookahead – Match Before Following Text
- Regex Negative Lookahead – Exclude a Following Pattern
- Regex Replace Capture Groups – Use $1 and $2 in JavaScript
- Regex Replace All – Use the JavaScript g Flag
JWT troubleshooting
JWT problems
Inspect JWT structure, Base64URL segments, JSON claims, time values, algorithms, key identifiers, and verification-related mistakes safely.
- JWT Wrong Segment Count – Fix Tokens with 2 or 4 Parts
- JWT Empty Segment – Fix Missing Header, Payload, or Signature
- JWT Invalid Base64URL Header – Fix Header Encoding
- JWT Invalid JSON Header – Fix Decoded Header JSON
- JWT Invalid Base64URL Payload – Fix Payload Encoding
- JWT Invalid JSON Payload – Fix Decoded Claim JSON
- JWT Expired Token – Decode and Check the exp Claim
- JWT Signature Not Verified – Decode vs Verify Explained
- JWT Missing exp Claim – Decode a Token Without Expiration
- JWT exp Claim Is a String – Fix a Non-Numeric Expiration
- JWT exp in Milliseconds – Fix an Expiration Date Far in the Future
- JWT iat Claim Is a String – Fix a Non-Numeric Issued-At Time
- JWT iat in the Future – Inspect a Future Issued-At Timestamp
- JWT exp Before iat – Fix Expiration Earlier Than Issued At
- JWT alg none – Decode the Header Without Trusting the Token
- JWT Missing alg Header – Why the Decoder Shows Algorithm Unknown
- JWT aud String vs Array – Understand Audience Claim Shapes
- JWT Missing aud Claim – Inspect a Token Without Audience
- JWT Missing iss Claim – Inspect a Token Without Issuer
- JWT Missing sub Claim – Inspect a Token Without Subject
- JWT nbf in the Future – Inspect a Future Not-Before Claim
- JWT nbf Claim Is a String – Fix a Non-Numeric Not-Before Time
- JWT Missing typ Header – Decode a Header Without typ
- JWT Missing kid Header – Inspect Key Selection Metadata
Query String troubleshooting
Query String problems
Resolve query-string parsing and building errors involving percent encoding, repeated parameters, empty values, fragments, arrays, and JSON inputs.
- Query String Plus Sign Becomes Space – + vs %2B Explained
- Repeated Query Parameters – Parse Duplicate Keys as Arrays
- Empty Query Parameter Value – Why name= Becomes an Empty String
- URL Fragment Ignored When Parsing Query String – # Explained
- Invalid JSON When Building Query String – Fix JSON Parse Errors
- Query String Builder Requires JSON Object – Fix Array or Scalar Input
- Nested JSON Object Not Supported in Query String – Flatten or Serialize Values
- Unsafe Integer in Query String JSON – Avoid JavaScript Precision Loss
- Percent-Encoded Ampersand in Query String – Use %26 Inside Values
- Equals Sign Inside Query Value – Decode %3D Correctly
- Percent-Encoded Unicode in Query Strings – Decode UTF-8 Values
- Malformed Percent Encoding in Query String – Why URLSearchParams Still Parses
- Empty Query Parameter Name – Why =value Creates an Empty Key
- Query Parameter Without Equals – Why ?debug Becomes an Empty String
- Percent-Encoded Query Parameter Name – Decode Spaces and Plus Signs in Keys
- Nested URL in Query Parameter – Encode & and = Inside Redirect URLs
- JSON Array to Repeated Query Parameters – Build Duplicate Keys
- JSON null in Query String – Why null Becomes an Empty Value
- Empty JSON Array in Query String – Why No Parameter Is Emitted
- Boolean Query Parameters – Build true and false from JSON
- Number Query Parameters – Build Integers and Decimals from JSON
- Empty String Query Parameter – Build key= from JSON
- Build Percent-Encoded Query String – Spaces, &, =, and Keys
- Unicode to Query String – UTF-8 Percent Encoding for Text and Emoji
Timestamp troubleshooting
Timestamp problems
Diagnose Unix and ISO timestamp mistakes involving seconds versus milliseconds, time zones, offsets, invalid dates, precision, and numeric formats.
- 10-Digit Unix Timestamp – Convert Seconds to Date
- 13-Digit Unix Timestamp – Convert Milliseconds to Date
- Negative Unix Timestamp – Convert Dates Before 1970
- Decimal Unix Timestamp – Convert Fractional Seconds
- Invalid Date to Unix Timestamp – Detect Impossible Calendar Dates
- ISO 8601 Date to Unix Timestamp – Convert UTC Date Online
- ISO Timestamp with Timezone Offset – Convert +08:00 to Unix Time
- Date Without Timezone to Unix Timestamp – VetaTool Uses UTC
- ISO Timestamp with Milliseconds – Convert Fractional Seconds
- Date Only to Unix Timestamp – Convert YYYY-MM-DD as UTC
- Timestamp +00:00 Offset – Is It the Same as UTC Z?
- Timestamp with Negative Timezone Offset – Convert -05:00
- Leap Day to Unix Timestamp – Convert February 29
- Unix Timestamp 0 – What Date Is the Unix Epoch?
- Unix Timestamp 2038 – Convert 2147483647 Boundary
- 11-Digit Unix Timestamp – Seconds or Milliseconds?
- YYYYMMDD to Unix Timestamp – Convert Compact Date
- YYYY/MM/DD to Unix Timestamp – Slash Date Format
- Timestamp Without Seconds – Convert YYYY-MM-DD HH:mm
- Timestamp Offset Without Colon – Convert +0800 ISO Time
- Timestamp Fractional Seconds Precision – Microseconds to Milliseconds
- Unix Timestamp Unit Threshold – When Does VetaTool Use Milliseconds?
- Unix Timestamp Scientific Notation – Why 1.7e9 Is Rejected
- Comma-Separated Unix Timestamp – Remove Thousands Separators
UUID troubleshooting
UUID problems
Check UUID text format, versions, RFC variants, nil values, wrappers, whitespace, punctuation, and version-specific validation failures.
- Invalid UUID Format – Check UUID Syntax Online
- UUID Without Hyphens – Why 32 Hex Characters Fail
- UUID with Braces – Remove { } Before Validation
- Invalid UUID Version – Check the Version Nibble
- Invalid UUID Variant – Check RFC 4122 Variant Bits
- Nil UUID – Is 00000000-0000-0000-0000-000000000000 Valid?
- Uppercase UUID – Are Capital Hex Letters Valid?
- UUID Version Detector – Check UUID v1-v8 Online
- UUID v2 Validation – Check Version 2 UUID Online
- UUID v3 Validation – Check Version 3 UUID Online
- UUID v4 Validation – Check Random UUID Format Online
- UUID v5 Validation – Check Version 5 UUID Online
- UUID v6 Validation – Check Version 6 UUID Online
- UUID v7 Validation – Check Version 7 UUID Online
- UUID v8 Validation – Check Version 8 UUID Online
- UUID with Spaces – Leading and Trailing Whitespace Validation
- UUID URN Prefix – Why urn:uuid: Fails Bare UUID Validation
- Quoted UUID String – Remove JSON or Code Quotes Before Validation
- UUID with Trailing Comma – Fix Copied CSV or List Values
- UUID with Internal Space – Why Whitespace Inside UUID Fails
- UUID Variant 8 – Validate RFC-Compatible Variant Nibble
- UUID Variant 9 – Check RFC-Compatible UUID Variant Online
- UUID Variant A – Validate Hexadecimal A Variant Nibble
- UUID Variant B – Check Upper RFC-Compatible Variant Boundary
Hash troubleshooting
Hash problems
Explain hash mismatches caused by algorithms, text encoding, whitespace, line endings, invisible Unicode, byte interpretation, and digest length.
- Hash Case Sensitive? Why Hello and hello Differ
- Leading Space Changes Hash – Whitespace SHA-256 Check
- Trailing Space Changes Hash – Hidden Whitespace Check
- Trailing Newline Changes Hash – echo vs printf SHA-256
- CRLF vs LF Hash – Why Line Endings Change SHA-256
- Tab vs Space Hash – Hidden Whitespace SHA-256 Difference
- Unicode Normalization Hash – Same-Looking Text, Different SHA-256
- MD5 vs SHA-256 Hash Mismatch – Check the Algorithm
- 32 Character Hash – Is It MD5? Digest Length Guide
- 40 Character Hash – Is It SHA-1? Digest Length Guide
- 64 Character Hash – Is It SHA-256? Digest Length Guide
- 128 Character Hash – Is It SHA-512? Digest Length Guide
- MD5 vs SHA-1 Hash – 32 vs 40 Character Digests
- SHA-1 vs SHA-256 Hash – 40 vs 64 Character Digests
- SHA-256 vs SHA-512 Hash – 64 vs 128 Character Digests
- Empty Hash Input – Why VetaTool Shows No Digest
- UTF-8 BOM Changes Hash – Invisible BOM SHA-256 Check
- Zero-Width Space Changes Hash – U+200B SHA-256 Check
- Non-Breaking Space vs Space Hash – NBSP SHA-256 Difference
- Emoji Hash SHA-256 – UTF-8 Character vs Unicode Escape Text
- JSON Whitespace Changes Hash – Minified vs Spaced JSON SHA-256
- JSON Key Order Changes Hash – Same Object, Different SHA-256
- Hash Hex String vs Bytes – Why 68656c6c6f Differs from hello
- Hash Base64 String vs Decoded Text – aGVsbG8= vs hello