Removed self-assignments (varname=varname) (closes #1081)
Separated inlining code (for inlining things into references, or removing IIFEs)
Allow multiple identifiers with the same name in var destructuring (eg var { a, a } = x) (#1176)

v5.13.0#

All calls to eval() were removed (#1171, #1184)
source-map was updated to 0.8.0-beta.0 (#1164)
NavigatorUAData was added to domprops to avoid property mangling (#1166)

v5.12.1#

Fixed an issue with function definitions inside blocks (#1155)
Fixed parens of new in some situations (closes #1159)

v5.12.0#

TERSER_DEBUG_DIR environment variable
@copyright comments are now preserved with the comments="some" option (#1153)

v5.11.0#

Unicode code point escapes (\u{abcde}) are not emitted inside RegExp literals anymore (#1147)
acorn is now a regular dependency

v5.10.0#

Massive optimization to max_line_len (#1109)
Basic support for import assertions
Marked ES2022 Object.hasOwn as a pure function
Fix delete optional?.property
New CI/CD pipeline with github actions (#1057)
Fix reordering of switch branches (#1092), (#1084)
Fix error when creating a class property called get
Acorn dependency is now an optional peerDependency
Fix mangling collision with exported variables (#1072)
Fix an issue with return someVariable = (async () => { ... })() (#1073)

v5.9.0#

Collapsing switch cases with the same bodies (even if they're not next to each other) (#1070).
Fix evaluation of optional chain expressions (#1062)
Fix mangling collision in ESM exports (#1063)
Fix issue with mutating function objects after a second pass (#1047)
Fix for inlining object spread { ...obj } (#1071)
Typescript typings fix (#1069)

v5.8.0#

Fixed shadowing variables while moving code in some cases (#1065)
Stop mangling computed & quoted properties when keep_quoted is enabled.
Fix for mangling private getter/setter and .#private access (#1060, #1068)
Array.from has a new optimization when the unsafe option is set (#737)
Mangle/propmangle let you generate your own identifiers through the nth_identifier option (#1061)
More optimizations to switch statements (#1044)

v5.7.2#

Fixed issues with compressing functions defined in global_defs option (#1036)
New recipe for using Terser in gulp was added to RECIPES.md (#1035)
Fixed issues with ?? and ?. (#1045)
Future reserved words such as package no longer require you to disable strict mode to be used as names.
Refactored huge compressor file into multiple more focused files.
Avoided unparenthesized in operator in some for loops (it breaks parsing because of for..in loops)
Improved documentation (#1021, #1025)
More type definitions (#1021)

v5.7.1#

Avoided collapsing assignments together if it would place a chain assignment on the left hand side, which is invalid syntax (a?.b = c)
Removed undefined from object expansions ({ ...void 0 } -> {})
Fix crash when checking if something is nullish or undefined (#1009)
Fixed comparison of private class properties (#1015)
Minor performance improvements (#993)
Fixed scope of function defs in strict mode (they are block scoped)

v5.7.0#

Several compile-time evaluation and inlining fixes
Allow reduce_funcs to be disabled again.
Add spidermonkey options to parse and format (#974)
Accept {get = "default val"} and {set = "default val"} in destructuring arguments.
Change package.json export map to help require.resolve (#971)
Improve docs
Fix export default of an anonymous class with extends

v5.6.1#

Mark assignments to the .prototype of a class as pure
Parenthesize await on the left of ** (while accepting legacy non-parenthesised input)
Avoided outputting NUL bytes in optimized RegExps, to stop the output from breaking other tools
Added exports to domprops (#939)
Fixed a crash when spreading ...this
Fixed the computed size of arrow functions, which improves their inlining

v5.6.0#

Added top-level await
Beautify option has been removed in #895
Private properties, getters and setters have been added in #913 and some more commits
Docs improvements: #896, #903, #916

v5.5.1#

Fixed object properties with unicode surrogates on safari.

v5.5.0#

Fixed crash when inlining uninitialized variable into template string.
The sourcemap for dist was removed for being too large.

v5.4.0#

Logical assignment
Change let x = undefined to just let x
Removed some optimizations for template strings, placing them behind unsafe options. Reason: adding strings is not equivalent to template strings, due to valueOf differences.
The AST_Token class was slimmed down in order to use less memory.

v5.3.8#

Restore node 13 support

v5.3.7#

Hotfix release, fixes package.json "engines" syntax

v5.3.6#

Fixed parentheses when outputting ?? mixed with || and &&
Improved hygiene of the symbol generator

v5.3.5#

Avoid moving named functions into default exports.
Enabled transform() for chain expressions. This allows AST transformers to reach inside chain expressions.

v5.3.4#

Fixed a crash when hoisting (with hoist_vars) a destructuring variable declaration

v5.3.3#

source-map library has been updated, bringing memory usage and CPU time improvements when reading input source maps (the SourceMapConsumer is now WASM based).
The wrap_func_args option now also wraps arrow functions, as opposed to only function expressions.

v5.3.2#

Prevented spread operations from being expanded when the expanded array/object contains getters, setters, or array holes.
Fixed very slow self-recursion in some cases of removing extraneous parentheses from + operations.

v5.3.1#

An issue with destructuring declarations when pure_getters is enabled has been fixed
Fixed a crash when chain expressions need to be shallowly compared
Made inlining functions more conservative to make sure a function that contains a reference to itself isn't moved into a place that can create multiple instances of itself.

v5.3.0#

Fixed a crash when compressing object spreads in some cases
Fixed compiletime evaluation of optional chains (caused typeof a?.b to always return "object")
domprops has been updated to contain every single possible prop

v5.2.1#

The parse step now doesn't accept an ecma option, so that all ES code is accepted.
Optional dotted chains now accept keywords, just like dotted expressions (foo?.default)

v5.2.0#

Optional chaining syntax is now supported.
Consecutive await expressions don't have unnecessary parens
Taking the variable name's length (after mangling) into consideration when deciding to inline

v5.1.0#

import.meta is now supported
Typescript typings have been improved

v5.0.0#

in operator now taken into account during property mangle.
Fixed infinite loop in face of a reference loop in some situations.
Kept exports and imports around even if there's something which will throw before them.
The main exported bundle for commonjs, dist/bundle.min.js is no longer minified.

v5.0.0-beta.0#

BREAKING: minify() is now async and rejects a promise instead of returning an error.
BREAKING: Internal AST is no longer exposed, so that it can be improved without releasing breaking changes.
BREAKING: Lowest supported node version is 10
BREAKING: There are no more warnings being emitted
Module is now distributed as a dual package - You can import and require() too.
Inline improvements were made

v4.8.1 (backport)#

Security fix for RegExps that should not be evaluated (regexp DDOS)

v4.8.0#

Support for numeric separators (million = 1_000_000) was added.
Assigning properties to a class is now assumed to be pure.
Fixed bug where yield wasn't considered a valid property key in generators.

v4.7.0#

A bug was fixed where an arrow function would have the wrong size
arguments object is now considered safe to retrieve properties from (useful for length, or 0) even when pure_getters is not set.
Fixed erroneous const declarations without value (which is invalid) in some corner cases when using collapse_vars.

v4.6.13#

Fixed issue where ES5 object properties were being turned into ES6 object properties due to more lax unicode rules.
Fixed parsing of BigInt with lowercase e in them.

v4.6.12#

Fixed subtree comparison code, making it see that [1,[2, 3]] is different from [1, 2, [3]]
Printing of unicode identifiers has been improved

v4.6.11#

Read unused classes' properties and method keys, to figure out if they use other variables.
Prevent inlining into block scopes when there are name collisions
Functions are no longer inlined into parameter defaults, because they live in their own special scope.
When inlining identity functions, take into account the fact they may be used to drop this in function calls.
Nullish coalescing operator (x ?? y), plus basic optimization for it.
Template literals in binary expressions such as + have been further optimized

v4.6.10#

Do not use reduce_vars when classes are present

v4.6.9#

Check if block scopes actually exist in blocks

v4.6.8#

Take into account "executed bits" of classes like static properties or computed keys, when checking if a class evaluation might throw or have side effects.

v4.6.7#

Some new performance gains through a AST_Node.size() method which measures a node's source code length without printing it to a string first.
An issue with setting --comments to false in the CLI has been fixed.
Fixed some issues with inlining
unsafe_symbols compress option was added, which turns Symbol("name") into just Symbol()
Brought back compress performance improvement through the AST_Node.equivalent_to(other) method (which was reverted in v4.6.6).

v4.6.6#

(hotfix release)

Reverted code to 4.6.4 to allow for more time to investigate an issue.

v4.6.5 (REVERTED)#

Improved compress performance through using a new method to see if two nodes are equivalent, instead of printing them to a string.

v4.6.4#

The "some" value in the comments output option now preserves @lic and other important comments when using //
</script> is now better escaped in regex, and in comments, when using the inline_script output option
Fixed an issue when transforming new RegExp into /.../ when slashes are included in the source
AST_Node.prototype.constructor now exists, allowing for easier debugging of crashes
Multiple if statements with the same consequents are now collapsed
Typescript typings improvements
Optimizations while looking for surrogate pairs in strings

v4.6.3#

Annotations such as /*#__NOINLINE__*/ and /*#__PURE__*/ may now be preserved using the preserve_annotations output option
A TypeScript definition update for the keep_quoted output option.

v4.6.2#

A bug where functions were inlined into other functions with scope conflicts has been fixed.
/*#__NOINLINE__*/ annotation fixed for more use cases where inlining happens.

v4.6.1#

Fixed an issue where a class is duplicated by reduce_vars when there's a recursive reference to the class.

v4.6.0#

Fixed issues with recursive class references.
BigInt evaluation has been prevented, stopping Terser from evaluating BigInts like it would do regular numbers.
Class property support has been added

v4.5.1#

(hotfix release)

Fixed issue where () => ({})[something] was not parenthesised correctly.

v4.5.0#

Inlining has been improved
An issue where keep_fnames combined with functions declared through variables was causing name shadowing has been fixed
You can now set the ES version through their year
The output option keep_numbers has been added, which prevents Terser from turning 1000 into 1e3 and such
Internal small optimisations and refactors

v4.4.3#

Number and BigInt parsing has been fixed
/*#__INLINE__*/ annotation fixed for arrow functions with non-block bodies.
Functional tests have been added, using this repository.
A memory leak, where the entire AST lives on after compression, has been plugged.

v4.4.2#

Fixed a problem with inlining identity functions

v4.4.1#

note: This introduced a feature, therefore it should have been a minor release.

Fixed a crash when unsafe was enabled.
An issue has been fixed where let statements might be collapsed out of their scope.
Some error messages have been improved by adding quotes around variable names.

v4.4.0#

Added /*#__INLINE__*/ and /*#__NOINLINE__*/ annotations for calls. If a call has one of these, it either forces or forbids inlining.

v4.3.11#

Fixed a problem where window was considered safe to access, even though there are situations where it isn't (Node.js, workers...)
Fixed an error where ++ and -- were considered side-effect free
Number(x) now needs both unsafe and and unsafe_math to be compressed into +x because x might be a BigInt
keep_fnames now correctly supports regexes when the function is in a variable declaration

v4.3.10#

Fixed syntax error when repeated semicolons were encountered in classes
Fixed invalid output caused by the creation of empty sequences internally
Scopes are now updated when scopes are inlined into them

v4.3.9#

Fixed issue with mangle's keep_fnames option, introduced when adding code to keep variable names of anonymous functions

v4.3.8#

Typescript typings fix

v4.3.7#

Parsing of regex options in the CLI (which broke in v4.3.5) was fixed.
typescript definition updates

v4.3.6#

(crash hotfix)

v4.3.5#

Fixed an issue with DOS line endings strings separated by \ and a new line.
Improved fix for the output size regression related to unused references within the extends section of a class.
Variable names of anonymous functions (eg: const x = () => { ... } or var func = function () {...}) are now preserved when keep_fnames is true.
Fixed performance degradation introduced for large payloads in v4.2.0

v4.3.4#

Fixed a regression where the output size was increased when unused classes were referred to in the extends clause of a class.
Small typescript typings fixes.
Comments with @preserve, @license, @cc_on as well as comments starting with /*! and /**! are now preserved by default.

v4.3.3#

Fixed a problem where parsing template strings would mix up octal notation and a slash followed by a zero representing a null character.
Started accepting the name async in destructuring arguments with default value.
Now Terser takes into account side effects inside class extends clauses.
Added parens whenever there's a comment between a return statement and the returned value, to prevent issues with ASI.
Stopped using raw RegExp objects, since the spec is going to continue to evolve. This ensures Terser is able to process new, unknown RegExp flags and features. This is a breaking change in the AST node AST_RegExp.

v4.3.2#

Typescript typing fix
Ensure that functions can't be inlined, by reduce_vars, into places where they're accessing variables with the same name, but from somewhere else.

v4.3.1#

Fixed an issue from 4.3.0 where any block scope within a for loop erroneously had its parent set to the function scopee
Fixed an issue where compressing IIFEs with argument expansions would result in some parameters becoming undefined
addEventListener options argument's properties are now part of the DOM properties list.

v4.3.0#

Do not drop computed object keys with side effects
Functions passed to other functions in calls are now wrapped in parentheses by default, which speeds up loading most modules
Objects with computed properties are now less likely to be hoisted
Speed and memory efficiency optimizations
Fixed scoping issues with try and switch

v4.2.1#

Minor refactors
Fixed a bug similar to #369 in collapse_vars
Functions can no longer be inlined into a place where they're going to be compared with themselves.
reduce_funcs option is now legacy, as using reduce_vars without reduce_funcs caused some weird corner cases. As a result, it is now implied in reduce_vars and can't be turned off without turning off reduce_vars.
Bug which would cause a random stack overflow has now been fixed.

v4.2.0#

When the source map URL is inline, don't write it to a file.
Fixed output parens when a lambda literal is the tag on a tagged template string.
The mangle.properties.undeclared option was added. This enables the property mangler to mangle properties of variables which can be found in the name cache, but whose properties are not known to this Terser run.
The v8 bug where the toString and source representations of regexes like RegExp("\\\n") includes an actual newline is now fixed.
Now we're guaranteed to not have duplicate comments in the output
Domprops updates

v4.1.4#

Fixed a crash when inlining a function into somewhere else when it has interdependent, non-removable variables.

v4.1.3#

Several issues with the reduce_vars option were fixed.
Starting this version, we only have a dist/bundle.min.js

v4.1.2#

The hotfix was hotfixed

v4.1.1#

Fixed a bug where toplevel scopes were being mixed up with lambda scopes

v4.1.0#

Internal functions were replaced by Object.assign, Array.prototype.some, Array.prototype.find and Array.prototype.every.
A serious issue where some ESM-native code was broken was fixed.
Performance improvements were made.
Support for BigInt was added.
Inline efficiency was improved. Functions are now being inlined more proactively instead of being inlined only after another Compressor pass.

v4.0.2#

(Hotfix release. Reverts unmapped segments PR #342, which will be put back on Terser when the upstream issue is resolved)

v4.0.1#

Collisions between the arguments of inlined functions and names in the outer scope are now being avoided while inlining
Unmapped segments are now preserved when compressing a file which has source maps
Default values of functions are now correctly converted from Mozilla AST to Terser AST
JSON ⊂ ECMAScript spec (if you don't know what this is you don't need to)
Export AST_* classes to library users
Fixed issue with collapse_vars when functions are created with the same name as a variable which already exists
Added MutationObserverInit (Object with options for initialising a mutation observer) properties to the DOM property list
Custom Error subclasses are now internally used instead of old-school Error inheritance hacks.
Documentation fixes
Performance optimizations

v4.0.0#

breaking change: The variables property of all scopes has become a standard JavaScript Map as opposed to the old bespoke Dictionary object.
Typescript definitions were fixed
terser --help was fixed
The public interface was cleaned up
Fixed optimisation of Array and new Array
Added the keep_quoted=strict mode to mangle_props, which behaves more like Google Closure Compiler by mangling all unquoted property names, instead of reserving quoted property names automatically.
Fixed parent functions' parameters being shadowed in some cases
Allowed Terser to run in a situation where there are custom functions attached to Object.prototype
And more bug fixes, optimisations and internal changes

v3.17.0#

More DOM properties added to --mangle-properties's DOM property list
Closed issue where if 2 functions had the same argument name, Terser would not inline them together properly
Fixed issue with hasOwnProperty.call
You can now list files to minify in a Terser config file
Started replacing new Array(<number>) with an array literal
Started using ES6 capabilities like Set and the includes method for strings and arrays

v3.16.1#

Fixed issue where Terser being imported with import would cause it not to work due to the __esModule property. (PR #254 was submitted, which was nice, but since it wasn't a pure commonJS approach I decided to go with my own solution)

v3.16.0#

No longer leaves names like Array or Object or window as a SimpleStatement (statement which is just a single expression).
Add support for sections sourcemaps (IndexedSourceMapConsumer)
Drops node.js v4 and starts using commonJS
Is now built with rollup

v3.15.0#

Inlined spread syntax ([...[1, 2, 3], 4, 5] => [1, 2, 3, 4, 5]) in arrays and objects.
Fixed typo in compressor warning
Fixed inline source map input bug
Fixed parsing of template literals with unnecessary escapes (Like \\a)